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user's manual

digital equipment corporation

BASIC/RT

USER'S

MANUAL

For additional c opies, order DEC~LB - U7~B~D from Program Library, Bldg.
1-2, Digita l Equ ipment Corporation, Mayna rd, Ma ss. 01754

Pri ce

$5. QO

First Pr i nting, July 1 971
Second Printing, August 1971

Your at t ention is invited to the last two pages of
this document. The "How to Obtain Software Information" page tells you how to keep up-to - date with DEC's
s o ftware. The "Reader 's Comments" page, when f illed
in and mailed, is beneficial to both you and DEC; a ll
comments r eceived are acknowledged and are cons idered
when documenting subsequent manuals .

1 9 71

Digital

Equipme nt

Corporation

The equipment descr i bed herein is covered by patents· .
and patents pending.

The followin g are trademarks of Digital Equi pment
Corporation, Maynard , Massachusetts:
DEC

PDP

FLIP CHIP

FOCAL

DIGITAL

COMPUTER LAB

OMNIBUS

UNI BUS

CONTENTS/'

INTRODUCTION

1.0

SCOPE COMMANDS

1.1

PLOT

1.2

DELAY

1.3

CLEAR

1.4

DISPLAY BUFFER

1.5

USE

2.0

CLOCK COMMANDS

2. 1

SET RATE

2.2

SET CLOCK

.2. 3

TIM

2.4

WAITC

2. 5

CLS AND CLC

3.0

A/D COMMANDS

3.1

ADC

3.2

REAL TIME

3.3

ACCEPT AND REJECT

3. 4

BUFFER CAPACITY

3.5

ADB

4.0

RESPONSE COMMANDS

4.1

TST

4.2

WAIT

5.0

USER COMMAND {UCOM)

6.0

USER CODED FUNCTION

APPENDIX A

COMMAND AND FUNCTION SUMMARY

A- 1

APPENDIX B

LOADING PROCEDURE

B-1

APPENDIX C

ERROR MESSAGES

C-1

Figure 1

CLOCK ENABLE REGISTER FUNCTIONS

iii

INTRODUCTION

BASIC/RT provides the researche r with a power fu l and complete software
package for total programmable control of all LABB /e peripheral de vices:

analog channels, Schmitt triggers, crystal clock and display

scope.

In addition, commands to specify parameters such as pulse rate

and response time permit optimum experi mental flexibility.

Buffer al-

location commands for the disp l ay and analog channels facil i tate computer efficiency.

Using the timing commands, a delay before sampling,

a pause until a user response is typed on the Teletyp~, or a pause until an interrupt occurs can easily be included in a program .

Another

feature, the user's command, permits customized system software.
Al l of the features provided by BK BASIC are also implemented in
BASIC/RT, permitting total programmable I/0 control and user coded
functions.

The entire BASIC/RT command and function set is included

in Appendix A of this manual.

For additional information on BASIC

fundamentals, refer to the EduSystem 10 System User's Guide; for details on 8K BASIC refer to the BK BASIC User's Manual, DEC- 08 - SKXA- D.
1.0

SCOPE COMMANDS

The display scope on the LAB8/e can be programmed to plot points on
its screen.

Th e scope commands provide complete control for ~raP.h

location and size, display time and number of points displayed .
l.l

PLOT

When plotting on the scope, wh ich is rectangular, BASIC/RT uses these
dimensions for its perimeter:
~<X<l.l
.~

~~Y<l.~

Thus, any plot must be within the above limits, which can easily be
accomplished by ins e rting a sca ling factor.
The PLOT command causes the appropriate point to be di spl ayed on
the scope.

It i s issued in the format:
PLOT

x,y

Teletype is a registered trademark of the Te l etype Corporation .

where x and y are any expressions which equal the actual X and Y co ordinate s of t he point to be plotted.

An acceptable sequence for p l ot-

ting a straight line across the middle of the scope is:
5

B=.5
FOR A=~ TO l.l STEP
PLOT A,B
NEXT A

1~
2~
3~

-~1

•

Remember that every X,Y set must be within the specified ranges.

it is not, that data set is simply not displayed.
PLOT commands can also be executed as direct statements.
plot a diagona l line from (.1,.1) to

(1.~,1.~),

Thus, to

t he f o l l owing sequence

c an be used:
FOR L= . l TO

1.~

STEP

.~~5'\..PLOT

L,L,NEXT L

BASIC/RT displays points on the scope when it is not doing any interna l calculations.

Data is displayed, for example, while wa i t ing for

i n put or outp ut.

If a cal culation is required during a p lott ing se-

quen ce, the da ta is not displayed until all the calculati ons are
c omp l eted.

Thu s, in the fo llowing example, plotting a decay i ng sine

wave, the function is not displayed until a l l the points have been
c a lcu l ated.
2~~
21~
22~

1. 2

FOR S=~ TO l.l~ STEP .~~ 6
PLOT S, SIN(S*35)*EXP( - S*2.5)/3+.5
NEXT S

DELAY

BASI C/RT provides a command that will refresh t he scope after e ach
c a l c ul ation so t hat the progress of the graph can be seen.

This com-

mand, DELAY, causes BASIC to displ ay all x,y points calcu lated up to
t his statement.

Thus, the decay of the sine wave above can be viewed

a f ter each point is calculated by adding to the above example the command
215

DELAY

The DELAY command provides the additional time for BASIC to display
t h e point before continuing to the next statement.

1.3

CLEAR

BASIC/RT also permits e rasing the scope under program control.

By in-

serting the statement :
CLEAR
all points currently displayed are removed from the screen.

Thus, if

more than one plot is required by a user program and it is not necessary for them to overlap, a CLEAR command between cal culations
erases the scope for the second plot.
In the next example, two compounded interest sums, $400 at 7% and $450
at 6 . 25% per annum compounded yearly f o r 30 years, are plotted .

the intercept point is to be noted, then line 12¢ can be omit ted and
at completion the two curves will be disp l ayed together.
1¢¢
1~2
1~4
11~
12~

I = - ~625
P = 4 5~
GOSUB 5~~

15~
5~~

STOP
FOR N=l TO T
X=N/35

55%
56~

1 .4

51~

GOSUB 5¢~
CLEAR

13¢
13 4
14¢
51~
52~
53~
54~

Lines

I=.~7
P=4¢~
T=3~

Y=(P*((I+l)tN)/4~¢~)

PLOT X,Y
DELAY
NEXT N
RETURN

and 52¢ inc l ude scaling factors f or the scope.

DISPLAY BUFFER

The technique for plotting points e mployed by BASIC/RT inc l udes c r ea ti ng a buffer in the user's area o f core to store a l l the calculate d
points before they are displayed.

[This buffer area is considered as

a dimensioned variable; thus, executi ng the commands SCRATCH, RUN, and
END removes the buffer from core.

The CLEAR command does not delete

the buffer, it merely e rases i ts contents.]

When a PLOT command is en-

countered BASIC/RT checks to see if a display buffer h a s al re ady been
assigned and if not, then space sufficient for about
allocated.

5%~

points is

If this amount of room i s not available in core, the error

message TOO BIG is p rinted.
3

1.5

USE

The area created by the PLOT command is approximately
dimens i onal array.

equal to a 333 -

In order to conserve space , if less than

a r e to be plotted, or to plot more than

5~~

po i nts

points , a b u ffe r d i mens ion-

ing c ommand is provided so that core can be allocat ed opt imally.

This

command, USE x, is implemented as an array, as follows ( x i s a l ways a
variable) :
2~
3~

Line

says :

DI M P(2~~)
USE P
use P as a storage buffer for a futu r e PLOT command; d o

not create a n addit i onal array at that time.
room for about 3~~ data points

•

Line

creates enough

I f a user- assigned or BAS I C/ RT gen-

erat ed buffer is not large enough and overflowed dur ing exe cution, the
error message TOO BIG is printed.
Only one USE statement is effective for any plot sequence and, if i t
is to be used, it must be issue d before t he PLOT command.

The var i -

ab l e associated with the USE command is ac t ive un til one o f t he buffe r
remov i ng stat ements (RUN, SCRATCH, END) is encountered, but i t can be
used for another purpose when not currently required for displaying.
In the example in section 1.3 the maximum number o f points t o be
plotted is

3~,

so a considerable amount of core can be cons erved by

speci fy i ng a sma l ler b u ffer.

The f ollowing code can be added to opti -

mize the program.
l~
2~

2.0

DIM M(4~)
USE M

CLOCK COMMANDS

The hardware clock provided in the LAB8/e, like all the other devi c e s,
can be handled under program control t o maximize its p erformance, by
specifying parameters such as pulse rate and initial pulse t i me.
1

To determine the minimum array size for point displays, cons ide r t hat
each point requires two values (X and Y) and t hat every thre e values
require one word of memory.
To display P points an array d i mensione d
for W words is necessary: W=.67(P).

2.1

SET RATE

To set the cloc k t o interrupt at a speci f ic rate, u s e the command
SET RATE mode,time
wh ere mode 1 is the des i red clock speed (0 - 7 ) and t ime i s the numbe r of
clock "ticks" between inte r rupts, up to 40 9 6 counts.
mode value is de r ived from the next chart.
mode

rate

0
1
2

Stop
external input
1,0- 2 seconds
10- 3 seco nds
1,0- 4 secon ds
10- 5 seconds
1,0- 6 second s
Stop

4
5

6
7

Thus, f or t he clock

The appropriate

to interrupt at 1 sec ond i nt erv als, a n acceptable

command i s
SET RATE 3, 10,00
which causes the clock to wait 1000 one msec. ti c k s.

If the

spec~fied

clock ra t e is too fast, so that t he interrup t cannot be servi ced i n
time, the error message RATE ERROR AT (line numbe r) is printed and t he
clock s t opped.

The line number printed is that of the s t atement cur-

rently being execut ed.
Not e that in t he 1 00- 20,0

~sec

elapsed total t ime ran ge BAS I C/RT is s e r -

v i cin g t h e i n ter rupt correctly, but is no t execu t ing a ny BAS I C/RT commands becaus e o f t he high rate; in this c a s e, t h e processin g h as b een
suspended.

Type CTRL/C, wh i ch wi ll cau s e the RATE ERROR mes s age to be

print ed, to restart .

2.2

SET CLOCK

BASIC/RT provi des another command for setting t he clock rate for the
Schmitt triggers.

Its for mat is fue same as that for the SET RATE com-

mand , namely
1

If an i l legal mode is requested, BASI C tri es to use the value: - 3 will
be taken as 3, .,03 as ,0, e t c.
2

Refer to DKB- EP Clock Description in the PDP - 8/e Smal l Computer Handbook.
5

SET CLOCK mode.time
except that mode is a 12-bit deci mal number which will be used to load
the c lock enab le register 1 , thus permitting the us er to enable any
function he chooses. Refer to Table l to determine t he appropriate
value. The time p a rameter is specified in t he same manner as with
t he SET RATE command. 2

Any time either of the SET statement s i s encount ered, the t ime c ounter
i s zeroe d. Then, any t ime a clock inte rrupt occurs, this counter is
incremented. ·up t o approximately 16 ,)1)1)1 ,)1)1)1 counts can occur b efore
this counter rese ts itself to ze ro.
2.3

TIM

At any time in the program, the current count (number o f e lap sed i n terrupts) can be determined v ia t he functi o n TI M(n ) .
This fu nctio n can be u sed in conjunction wi t h any o f t he BASIC c ommands so tha t the value can be printed or the next actio n t o be perf ormed by the p ro g r am can be dependent on the count . The for mat o f
the function call is TIM(n) where n is any argument (the argume nt is
not checked by BASIC/ RT ). In the following pr ogra m the elapsed,time f o r
the plot determines the nex t action; prin t t he count and halt or, f o r
5)1 data po ints, p ri nt the sines and th e termina ting count and then stop.
In the firs t run, t he time e lap sed .
table was generated.
1)1 A=l)1
2)1 SET RATE 2 ,2)1
3)1 FOR M=)1 TO l STEP .)11
4)1 PLOT M,Mt2
5)1 DELAY
6)1 NEXT M
7)1 IF A> TIM ()1) THEN 2)1)1
8)1 PRINT TIM ( 23)
9)1 STOP
2)1)1 FOR Z=)1 TO l STEP .)52
21)1 PRINT SIN(Z)
22)1 NEXT Z
23)1 PRINT TIM(C)
24)1 END
1

By changi ng line 1)1, the sine

RUN
1)1
READY.
1)1 A= l 2
RUN
)1
.)119998 67
.)13998933

BAS I C/RT a l ways forces the interrupt req ues t bit on .

The 2's comp l ement of the value of time is perfo rmed so that i t is
in a f o rm suitable f or the clock.
6

•

TABLE J
CLOCK ENABLE REGISTER FUNCTIONS

AC Bit

Function
Enables clock overf l ow to cause an interrupt .

1 & 2

3r 4

Mode

Counter runs at selected rate . Overflow occurs
every 4~96 counts.
Flag remains set .

Counter runs at selected rate. Overflow causes
Clock Buffer to be transferred to the Clock
Counter, which continues to run. Ove rflow remains set until cleared with IOT 6135 .

Counter runs at selected rate . When an enabled
event occurs, the Clock Counter is transferred
to the Clock Buffer, and the Counter continues.

Counter runs at selected rate. When an enabled
input occurs on channe l 3, the Clock Counter is
transferred to the Clock Buffer, and the Clock
Counter continues to run from zero.

Count Rate
111
ll~

1~1
l~~
~ll
~l~
~~1

~~~

Stop
l MHZ
l~~ KHz
l~ KHz
l KHz
l~~ KHz
External input
Stop

Overflow starts ADC.
(When the Clock Counte r overflows,
the analog-to-digital converter, type AD8-EA is started.)

When s et · to a l, th e Crystal Clock i s inhibited fro m
generating clock pulses that incremen t the counte r.

Even ts in Channels l, 2, or 3 cause an interrupt re quest.

1~,

& 11 Enabl e Events 1, 2, and 3
9
1~

Event 3
Event 2
Event 1

•
7

2. 4

IVAIT C

Another a pplication of the clock is t o halt progra m execution u ntil a
clock inter r upt occurs .

The WAITC command pe rfor ms t his function,

thereby p ennitting BAS I C/RT to display on the scope while waiting f or
the inte rr upt to signal continua tion of program execution .
2..5

CLS AND CLC

There are two oth er f unct i ons that are used with t he Schmi tt Triggers .
The first, CLS(n), obtains the status bits of the clock after the previous interrupt (those obta i ned from t h e PDP-8 CLS A (Clock Status to
ACI instruction).

This value can b e tested , for example, to determine

how the interrupt occurred .

The o t her, CLC(n), performs a CLCA

(Counter to b u ffer to AC) and returns the value a s a floating point
n umbe r.

Refer to PDP-8/e Smal l Computer Handbook.

3.0

A/D COMMANDS

3.1

ADC

Any A/D channel can be sampled at any time by using t h e si ngl e f unc tion ADC(n), whe re n is the channel numbe r , ~ to 15, to be sampled, in
a direct o r indirect statement. The ADC function performs arr· i"I1U1lediate conversion; the clock, however, can b e incorpora ted so t hat sampling occurs at an estab l ishe d clock

rate.

In the next prog r am ,

BASIC/ RT wa its for a clock tick a nd t hen prints the value of the clock
usi ng the TIM f u nction, and of A/D c hannels 3 and 4 for
3~~
3 1~
32~

32 1
322
323
33~

34~
35~

3. 2

samp les .

SET RATE 2,6~
FOR P=l TO 5~
WAIT C
Al =ADC(3)
A2=ADC(4)
Tl = TIM(~)

PRINT Tl,Al,A2
NEXT P
STOP

REAL T IME

The ADC f unct i o n i s r estricted to non-time critic al work becaus e t h e
fin ite amount o f t ime e l aps e d between c l ock ticks may not be s uffici en t t o p erform th e t asks reque s ted between ticks (for example, printing 3 values above) .

Also, more than one channe l canno t b e samp led
8

in the same time quanta (for example,

~~mpli ng channels 3 and 4

a bove).
For time cri tical operations , the REAL TIME command should be used
because it provides a buffer to hold the sampled value p r ior to processing.

Its format is :
REAL TIME v,cl,nl,n2

where v is a subscripted variab l e to be used as the data buffer.

The

variable is assigned in a manner analo gous to the US E command for the
scope , namely, as a dimen sioned array.

Because only one value is to

be taken per sample, three s amp les a re stored per buffer word.
a dimension of

1~~

can store

3~~

data i tems.

mensioned larger than approximately
2,2~~

po i nts.

Thus,

The array cannot be di -

or a maximum of approx i mately

75~,

The paramete r Cl is the f i rst channel to be sampled,

nl is the number of cons ecut ive channels to be sampled, and n2 is the
number of c lock ticks for which to sampl e .
nels 1 and 2 once every millisecond for

15~

To prepare to sample chanmilliseconds, suitable

code is :
SET RATE 4 ,1~
DIM G(l~~)
REAL TIME G, 1,2,15~
Operation of the REAL TIME command i s indepe nde n t of the BAS I C/RT
statement proc essing speed;

as long a s there i s su ff icient buffer

space , the REAL TIME statement wi ll work.
3.3

ACCEPT AND REJECT

The REAL TIME statement only creates the specified data bu f fer.

actually initiate sampling, the statement ACCEPT i s required.

Then

sampling will start a t the next clock tick.
REAL TIME statement or the ACCEPT is ignored.

There mus t be an active
A REAL TIME command be-

comes ina ctive whe n the clock count equal s zero.
use the command REJECT.

To s uspend sampling

This command is also use f ul for executing

subsequent REAL TIME stateme n ts.
In the nex t exampl e, the ACCEPT and REJECT statements a re used to be
sure sampling occ urs at the speci f i ed rate fo r only the d es i gnated
number of co un t s .

St a tement

5~~

stops the clock.

53~

prepares it so

t hat the fir s t sample is taken after processing statement

54~.

The

REJECT at 560 assures that after 100 coun ts no extra samples are taken
at the rate o f 10 mseconds .
LIST
500 SET RATE 7,0
510 DIM G(l00)
520 REAL TIME G,l,2,150
530 ACCEPT
540 SET RATE 2,10
550 IF TIM(4) < 100 THEN 550
560 REJECT
570 SET RATE 3,10
580 ACCEPT
590 END
3.4

BUFFER CAPAC ITY

In the last REAL TIME example, the buffer, G, is subsc ripted to accommodate 3*100=300 items.

The program, however, co uld have been required

to sample a greater total number of points.

If the 520 was REAL TIME

G, 1,6,150 then a total of 6*150=900 items must be accommodated .

handle this variation without having to allocate large a moun ts of core
as buffer space, BASIC/RT uses a ring buffer so that data can be removed
from the buffer before it is overwritten by a new, incoming item.

meet this c ondition, the s ampling can be:
1.

At a slow rate for a long time (consistent ti me
or

At a f ast

samp l~n g)

rate for a short time .

If a fast ra t e is required for a long er period, a larg e buffer can be
created, provided this space is not r equi red by BASIC/RT for variables,
etc.

If the buffe r becomes completely ful l such that da ta is being

overwritten, the message A-D FULL is printed.
rate is about 4KHz or 250

~s .;

The maximum t hroughput

the steady state long term ra t e i s

about 50 points/second.
3.5

ADB

To ret ri eve data collected by REAL TIME and ACCEP T sequence s t hat are
placed in a buffer, the ADB(n) function is requir ed .

Data is withd rawn

from the buffer in th e same order i n which it was e n tered.

Thus, if

fou r A/D channels, 1 - 4 , are being sampled, the order of the data in
the buffer is

•
10

The argument in the ADB funct ion is ign~red. The items will be r emoved
consecutively. If there is no REAL TIME or ACCEPT statement or i f
there is no data remaining in the buffer (because the number of clock
ticks, n2, in the REAL TIME statement had expi r ed), the error message
NO A- D and a line number are printed.
This example is an expansion of the one in section 3 .3 to incorpo rate
the ADB function. Lines 59~ through
sampled values can be printed.
5~~
51~
52~

53~
54~
55~
56~
57~
58~
59~
6~~
61~
63~

61~

have been added so that the

SET RATE 7,~
DIM G(l~~)
REAL TIME G,l , 2,15~
ACCEPT
SET RATE 2,1~
IF TIM(4) < l~~ THEN 55~
REJECT
SET RATE 3,1~
ACCEPT
FOR A=l TO 15~
PRINT ADB(l) ,ADB(2)
NEXT A
END

The user must kee p track of the items in the bu ffer (number requested
and number removed) and their ordering by channel number. In the
above example there will be 75 lines printed, e ach with two data
values i n the format:
1.
l

2.
l

If line 14~ was PRINT ADB(~) ,ADB(6) ,ADB (2) , the information printed
wou ld be in the order:
1.

2 i+l

1 i+2

1 i+3

4. 0

RESPONSE COMMAN OS

4.1

TST

For automated environments requiring a response typed on the Teletype
to determine the subsequent action, a testing function, TST(n), is
available which checks the Teletype to see if a character has been
typed.

If i t has, a non-zero is returned; if it has not , a zero is

returned.

The TST function is particularly handy in conjunction with

the TIM function

for~ecifying

a maximum response time.

tion must be reset by doing a GETC function

The TST func-

for the TST statement to

oe used more than once in a program.
4.2

WAIT

If a pause time is required by a program, the WAIT command can be included in the program.
terrupt occurs.

BASIC/RT processing will be halted until any in-

Note that a clock interrupt is sufficient to reacti -

vate BASIC/RT.

5. 0

USER COMMAND [UCOM]

The USER COMMAND is a feature in BASIC/RT which allows the user to insert his own code and to effective l y communicate with BASIC/RT.

This

command differs from the UUF funct ion in that it is more sophisticated
and hence more complicated in its operat ion .
differe nces:
command.

To briefly explain the

UUF is a function, such as SIN and COS, while UCOM is a

A function takes an expression in parentheses as its argu-

ment and returns a value to be used later.
takes 4.5 and re t urns 4.0.

For exampl e, Y=INT(4.5)

A command is a statement which may take

arguments (such as READ or INPUT) , o r may not have any (such as CLEAR
or END), or they may be optional (as with PRINT).

In a function such

as UUF, BASIC/RT has already evaluated the expression and left the results in the FAC before calling
control over what is i n it .

the function so the function has no

With a command, it is up to the user code

to scan and determine what is wanted.

To successfully use t h is com-

mand , a know l edge of PDP - 8 code and the floating point package is es sential.

It is suggested that the coding for commands such as CLEAR,

PLOT, USE,

(and any others) be studied in orde r t o understand the

nature of the commands.

Some brief examples a r e illustrated next to

show how to insert ~me simple commands.
In this example, a UCOM is created such tha t whenever it is i ssued, it
will execute a 6123 (some random IOT) with the AC al l 7's.
t hing to do is allocate space.

The first

There is room i n upper and lower core .

In this case, let us overlay the EXP function with the UCOM.

Put a

pointer in the execute table to the location of the command.

The table

entry will be about location 3~6
location).

(refer to a l isting for the exact

Now, whenever a UCOM is given, control will trans fer to

where this location points .

The code wil l t h e n loo k like:

*EXP
CLA CMA
6123
CLA
JMP I (DEVCOM

/Se t the AC t o all 7's
/Execute the lOT
/Clear the AC
/and conti nu e with BASIC

The routine DEVCOM checks to s e e that the next item on the li ne is a
C.R.

(carriage re turn).

given.

If i t is not, then an e r ror message will be

This is to prevent illegal user code from getting through :

UCOMING HOME FOR DINNER?

The

previuu~

~entence

would ca l l the UCOM

processor , but since the next item is not a C.R . , an error message··
would be given.
There are two more routines that can be used :

DEVCON and SKIPIT.

DEVCON does the same thing as DEVCOM except that i t checks the p r esent
item for C.R. rather than the next item.

SKI PIT will skip past the

rest of the line until it finds a C.R . a nd wi l l never give an error
message.
Now let us modify the previous exampl e .

This time let us g i ve t wo ex-

pressions and multiply the two together and t h en send out the low 12
order bits to the device via a 6123.

The command would look like:

UCOM A,B
where A and B are any expressions.

The codi ng is:

*EXP
J MS
J MS I
FENTER
FSTA
FE XI T
JMS I
FE NTER
FMU
FE XI T
J MS I
CLA
TAD
6123
CLA
JMP I

GETWD
(MEVAL

/ski p p a st t h e UCOM element .
/ e valu a te next eleme nt of line.

TEMP

/ save a way

( MEVAL

/e valuate next e lemen t of li ne .
/ e n te r t h e FPP package .
/ multip ly A*B.
/exit now .
/fi x t he AC n ow .
/clear the AC.
/p i c k u p l ow wo rd .
/ send to the devi ce .

TEMP
(FIX
AC3
(DEVCON

/and exit.

Notice t hat the exi t is vi a DEVCON rather than DEVCOM .
~lliVAL

cause

Th i s is be-

has evaluated the exp ress ion until it found a de l i mite r .

This mu s t be a comma in the f i r st place a nd a C. R. in the s e c o nd p l ace .
I f it is not, then DEVCON wil l g i ve a n e rro r mess a g e .

As s t ated p re-

v iously, the user should l ook at PLOT and USE a n d p erhaps a few othe r
commands to full y a ppreci a te the UCOM c ommand.
I t i s possible to put the UCOM code i n field l with only s ome minor
c hanges.
in

3~6

Since some c ommands a r e d isp a tched a gai n i n f ield 1, place

a p ointer t o 7743 .

(7743 i s the upper cor e dispa t cher . )

i n field l at 744, p l ace the addres s of the UCOM command cod e .
UCOM , BASIC/RT will now go to t h is loc a t i o n in fi e l d l .

The n ,
On

Cros-s "field

communication is done thr o ugh a var iety o f f u ncti o n s , all of which are
mentioned in the i nte rnal docume n tati o n .

The no v ice u s er i s a dvi sed

a gainst putting i nstructions in fi e l d 1 until he has succes s f u lly r un
functions and commands from field
side i n field l .

No t e that functi ons c a n al s o re -

The user should exami n e

ACCEP T , T I M, and po ssibly

REAL TIME to get a better un derst and ing o f cross -fi e l d c ommu ni c a tion s .
It i s possible t o a l loca te mo re sp a ce i n fi e ld 1 for f unc tio ns / c ommand s
by chang i ng the value o f LIMIT.
core used by BASIC/RT .
abou t

1 ~~~

LIMIT is t he first loc at i o n o f upper

By changing PLIMIT at 25 62 to, s ay,

2~ ~~ ,

8 locat i ons are g a inedbr use r f un c tio ns and commands .

that t his space is lost from the use r

p r og ram~ d

No t e

v ar iable area , but

very often this is worth the s acrifice.

6. 0

USER CODED FUNCT I ON

As i n 8K BASI C, the user can i nclude his o wn f unction i n BAS I C/ RT,
calling it a s UUF(n), to perf orm a spe cial t a sk .
14

Th e UUF functi o n is

coded i n t he same manne r as described in t he 8K BASIC User ' s Manual ,
except that the s ugg e sted l ocat i ons for the code a re 0 0 6 4 to 0 177 in
field 1.

Other sma ll e r areas are a vai l able in fi e l d 0 a nd many more

can b e c reated by delet i ng some of t he mathema tical fu n ct i ons.

- -- - -- - - - - - - - - - - - - - - -

APPENDIX A
COMMAND AND FUNCTION SUMMARY

A.l

••

Statements
ACCEPT

Start A/C sampling

CLEAR

Erase Scope

DATA

Provide initial data for a program

DEF

Define a fu nction

DELAY

Display scope buffer

DIM

Define subscripted variables

END

End a prog ram

FOR TO
STEP

Set up a program loop

GOSUB

Go to a subroutine

GOTO

Change order of program execution

IF THEN

Conditionally change order of program execution

IF THEN nn

Conditionally execute the statement nn

INPUT

Get variable values from the terminal

LET

Assign a value to a variable (LET is optional)

LPT

Assign line printer as output device

End a program loop

PLOT X,Y

P lot onfue scope the point x,y

Print out the ind ic ated information

PTP

Assi gn high speed paper tape punch as output device

PTR

Assign high speed paper tape reader as input device

READ

Initialize variables to value from the data l i st

REAL TIME

Create buffer fur A/D samples

REJECT

Stop A/D sampl ing

REM

Insert a program comment

RESTORE

Restore the data list

RETURN

Return from a subroutine

SET CLOCK

Set clock enable register

SET RATE

Set c lock interrupt rate

STOP

Stop program execution

TTY IN

Assig n Te letype as input device

TTY OUT

Assign Te letype as out put device

USE

Specify a d isplay buffer

WAIT

Pause

WAITC

Delay prog ram execution until next clo ck interrupt

execution un til next interrupt

A- 1

A. 2

Edit and Control Commands
LIST

List all stored program statements

RUB OUTS

Enable RUBOUT key

NO RUBOUTS

Disab l e RUBOUT key

RUN

Run the currently stored program

SCR

Delete the currently sto r ed progr am

CTRLIC

Stop execution and return to 8K BASIC
Stop output I Resume output

CTRLIO
A. 3

A. 4

Functions
SIN (X)

Sine of x (x in radians)

COS (X)

Cosine of x (x in

TAN (X)

Tangent of x (x in radians)

ATN(X)

Arctangent of x

EXP (X)

ex= (e=2 . 718282)

LOG (X)

Natural log of x

SGN (X)

Sign of x

INT (X)

Integer value of x

ABS (X)

Absolute value of x

SQR(X)

Square root of x

radians)

(x in radians )

RND (X)

Random number

GET (X)

Get a character

PUT (X)

Put a character

TAB(X)

Print next charac ter at space x

UUF(X)

User coded function (PDP-8 code)

FNA(X)
ADB

Use r defined function (8K BASIC)
Re tr l eve data from AID Buffer

ADC

Samp le AI D Channel

CLC

Obtain Trigger Counter

CLS

Obtain Clock Status Bits

TIM

Determine current clock count

TST

Check for character f rom Teletype

Ari t hmetic Operators

Addition
Subtraction

Multiplication

Division

Exponentiation

A-2

•

A.S

Relational Operators

In a LET (equate statement) a relational operator returns a
1 if true.

0 if false,

In an IF statement, i t establishes the condition of trans-

fe r .
=

equal to

less than

=<,

less than or equal to

greater than

=> 1 >=

greater than or equal to

< >

not equal to

A- 3

APPENDIX If/
LOADI NG PROCEDURE

Use t he following procedure tobad BAS IC/RT.
1.

Load the RI M lo ader into fi e ld l.
reader may be used.

Setfue data a nd instruc t i ons fields to l

the EXTD ADDR LOAD key)
tion.

Ei t he r t he high or low s peed
(use

before toggling i n t he first ins truc-

Note that after pressing DEP or EXAM, the LAB8/e a l ways

indicates the Program Counter location, n ot
l ocation, in t he upper row of l igh ts.

the Memory Address

To see what conten t has

j ust been l oad e d , set the mul tiple register knob to MD (Memo ry
Buf f er).
2.

Load the BIN loader into instruction fie l d l .

(Use the EXTD

ADDR LOAD key to load in thi s field setting.)
Steps l
3.

an d 2 c an be rep l a ced by l oading the HELP Bootstrap .

Read in the BASIC/RT paper tape .
tion field l.

~"lhen

Use data field l and instruc-

loading via the BIN l oader , press START

CLEAR then START CONT to i niti ate reading i n the tape .
4.

I f the AC =~ ( adjust the multip l e register k nob ) after loadi ng
BASIC/RT , t h e program can be s tarted .

Load in~~~~ with the

EXTD ADDR LOAD key then t h e start i ng add ress
LOAD key.

l ~~~

with t h e ADDR

BASIC/RT has its own field settings punche d on the tape so i t .
is not neces sary to set them i n the switches .

Press START

CLEAR then START CONT a n d BAS I C/ RT will indicate it is r eady .

B-1

APEENDIX C
ERROR MESSAGES

The computer checks all commands before executin g t hem.
reason

If for some

it cannot execute the command, it reports the fact by typing

one of the following messages.

The number of the line in which the

e rror was found is also typed out .
SYNTAX ERROR

The command does not corr e spond to the language
synt a x . Common examples of synta x errors are
misspe lled commands, unmatched parentheses, and
other ty pographica l e rrors .

:FUNCTION ERROR

A function was used which was deleted when the
system was loaded and hence is not avai l able .
A DEF statement will produce this error i f the
DEF capacity has been deleted .

TOO- BIG ERROR

The combination of program and variables ex ceeds the capacity of the computer.
Reducing
one or the other may help.
If the program has
undergone extens ive revision, try punching it
out, typing SCRATCH, and r eloading.

SUDSCRIPT ERROR

A subscript has been us ed which is o uts i de the
bounds defined i n the DIM statement.

LINENO ERROR

A GOTO, GOSUB, or IF references a nonexistent
line.

FOR ERROR

FOR l oops are nested too deeply .

NEXT ERROR

FOR and NE XT statements are not properly
paired .

GOSUB ERROR

Subroutines are nested too deepl y .

RETURN ERROR

GOSUB and RETURN statements
pai red.

DATA ERROR

There are no more items in the data line.

ARGUMENT ERROR

A fun ction has been given an illegal argument,
for example SQR(-1).

RATE ERROR

Clock r a te too fast to service interrupts.

A-D FULL

No more room in data buffer for remaining
items

NO A-D

No input coming fr om speci f ied analog channel.

c- 1

are not properly

I NDEX

ACCEPT funct i on, 9, l l
A/D channel samp l ing,
8
A/D comma nds,
8
ADB function, 10, ll
ADC function,
8
Arithmetic operators , A-2
BIN loade r, B-1
Buffer capacity,

Channel sampling, 8
CLC function,
8
CLEAR command,
3
Clock commands, 4
Clock enable r egister functions, 7
CLS function,
8
Commands,
clock, 4
definition , 12
edit and con trol, A-2
response, 12
scope, l
summary of, A- 1
use r , 12
Commands (summary in Appendix A)
CLEAR, 3
DELAY,
2
END , 3,4
PLOT, l , 4
REAL TIME
8
REJECT, 9
RUN,
3,4
SCRATCH,
3I 4
SET CLOCK, 5
SET RATE, 5
USE, 4, 9
WAIT, 12
WAITC,
8
Coordinates of poin t , 2
Cross field communication, 14
I

DELAY command,
2
DEVCOM routine, 13
DEVCON routine, 13
Dimensions of scope,
Display buffe r,
3
Display time,
l

Function
clock enab l e register,
7
definiti on, 12
summary A-1
user coded, 14
Functions (summary in Appendix A)
ACCEPT, 9
ADB, 10, l l
8
CLC,
CLS,
8
EXP I
13
REJECT , 9
TIM, 6, 8
TST·, 12
UUF, 14
GETC statement,
Gr aphs, l

Loading procedure,

B- 1

Operat ors, A- 2, A-3
Perimeter d i mensi ons of scope,
PLOT command, l , 4
P l ottinq, l
Points
coordinates, 2
displayed, number of, 2
plotting, 3
RATE ERROR error message, 5
REAL TIME command, 8, 9
REAL TIME statement, ll
refreshing s cope , 2
REJ ECT comman d, 9
Relationa l operators, A- 3
Response commands, 12
RIM loader, B-1
Routi nes
DEVCOM, 13
DEVGON, 13
SKIP IT, 13
RUN command,
3, 4

Sampling A/D channel,
Edit and cont r o l commands, A- 2
rate, 10
Scaling fac tor, l
END command, 3, 4
Schmitt triggers, 8
Erasing scope,
3
Error message (summary in Appendix C) Scope
commands, l
RATE ERROR, 5
eras i ng,
3
TOO BIG, 3, 4
refreshing, 2
EXP function, 13
I-1

8, 9

- - -- - - - - - - - - - -

SCRATCH command,
3, 4
SET CLOCK command,
5
SET RATE command ,
5
SKIPIT routine ,
13
Statement, GETC , 12
Statement summary, A- 1
Summary, commands and functions ,

UCOM command code, 1 2 , 1 3, 14
USE command,
4, 9
User coded fun ction, 14
User command,
12
UUF function, 12, 14
A-1
WAIT command, 12
WAITC command,
8

TIM function,
6, 8
TOO BIG error message,
TST function,
12

3, 4

X,Y coordinates,

I- 2