M7223

This document is an Engineering Change Order Log from Digital Equipment Corporation for the M7223 DP11 Control module, part of the PDP-11 Family. It outlines four engineering changes (FCOs) implemented between September 1971 and June 1973 to address various issues and improve the module's functionality and maintainability.

The key changes include:

• M7223-C0001 (Sep-71): Corrected an issue where SYNC extension bits (8-12) were improperly decoded, preventing them from being read to the bus. The fix involved modifying select decoding gates, requiring immediate in-plant rework and field rework if DP11-CA is installed.
• M7223-C0002 (Dec-71): Addressed a problem where the MOVB instruction was not decoded for loading the transmitter. The solution involved changing an IC (from 7400 to 7410) and specific pin connections. This change had to be installed in conjunction with FCO DP11D-C0005, affecting production units from January 1972 and field units for DP11-D operation.
• M7223-C0003 (Aug-72): Resolved the premature clearing of the OVERRUN condition (two character times after setting), which affected overloaded systems. The correction involved modifying logic to latch O'RUN and RX DONE flip-flops against further clocking inputs, with rework required for all field M7223s.
• M7223-00004 (Jun-73): Addressed potential part availability issues for DEC 380 bus receiver chips. The solution designated the 11380 IC (#19-11113) as an allowable substitute for the DEC 380 (#19-09485), with the stipulation that both types cannot be mixed in the same option. This was primarily a documentation/design change requiring immediate updates to the Allowable Substitution List.

Each entry details the specific problem, the technical correction, and the effectivity (when and where the change should be applied, including estimated installation times).