KW11-P programmable real-time clock manual

This manual describes the KW11-P Programmable Real-Time Clock, an optional quad-height module for the PDP-11 System. Its primary function is to accurately measure time intervals, provide programmed real-time interval interrupts, and count intervals in various modes. This hardware solution enhances system efficiency by offloading interval counting from the main processor.

Key functional units include:

• 16-Bit Synchronous Up/Down Counter: Counts at four selectable rates, can be read during operation, and initiates interrupts at zero (underflow/overflow).
• 16-Bit Count Set Buffer: Stores preset interval counts and reloads the counter automatically in repeat-interrupt mode.
• 9-Bit Control and Status Register: Manages various control and status signals for the buffer and counter.
• Clock: Provides crystal-controlled 100 kHz and 10 kHz signals, line frequency (50/60 Hz), and an external analog input, selectable via a multiplexer.
• Gating Control: Manages I/O signal access.
• Interrupt Control: Allows the KW11-P to become the bus master and generate interrupts, similar to the M782 Interrupt Control Module, sending a vector address (default 104) to the processor.
• Address Selector: Decodes bus address information for the Control and Status Register (772540), Count Set Buffer (772542), and Counter (772544).

The KW11-P supports three selectable modes of operation:

1. Single-Interrupt Mode: A preset time interval is counted, generating one interrupt at underflow/overflow, then stopping the clock and resetting the counter to zero.
2. Repeat-Interrupt Mode: Generates repeated interrupts at a rate corresponding to a preset time interval. The counter reloads automatically from the buffer after each underflow/overflow, and the clock restarts.
3. External-Event Counter: Uses an external input to clock the counter to determine the number of events.

The document also details the installation procedure, which involves connecting the LTC L signal from the power supply, and provides programming examples for software control of the KW11-P in its various operational modes.