54ACT818 Datasheet, PDF (1/10 Pages) National Semiconductor (TI) – 8-Bit Diagnostic Register

September 1998
54ACT818
8-Bit Diagnostic Register
General Description
The ’ACT818 is a high-speed, general-purpose pipeline reg-
ister with an on-board diagnostic register for performing se-
rial diagnostics and/or writable control store loading.
The D-to-Y path provides an 8-bit parallel data path pipeline
register for normal system operation. The diagnostic register
can load parallel data to or from the pipeline register and can
output data through the D input port (as in WCS loading).
The 8-bit diagnostic register has multiplexer inputs that se-
lect parallel inputs from the Y-port or adjacent bits in the di-
agnostic register to operate as a right-shift-only register. This
register can then participate in a serial loop throughout the
system where normal data, address, status and control reg-
isters are replaced with ’ACT818 diagnostic pipeline regis-
ters. The loop can be used to scan in a complete test routine
starting point (Data, Address, etc.). Then after a specified
number of machine cycles it scans out the results to be in-
spected for the expected results. WCS loading can be ac-
complished using the same technique. An instruction word
can be serially shifted into the shadow register and written
into the WCS RAM by enabling the D output.
Features
n On-line and off-line system diagnostics
n Swaps the contents of diagnostic register and output
register
n Diagnostic register and diagnostic testing
n Cascadable for wide control words as used in
microprogramming
n Edge-triggered D registers
n Outputs source/sink 24 mA
n ’ACT818 has TTL-compatible inputs
n ’ACT818 is functionally- and pin-compatible to AMD
Am29818 and MMI 74S818
n Standard Microcircuit Drawing (SMD) 5962-9160901
Applications
n Register for microprogram control store
n Status register
n Data register
n Instruction register
n Interrupt mask register
n Pipeline register
n General purpose register
n Parallel-serial/serial-parallel converter
Logic Symbol
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