54ACT818 Datasheet | National Semiconductor

Description .. The ’ACT818 is a high-speed, general-purpose pipeline register with an on-board diagnostic register for performing serial 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 select parallel inputs from the Y-port or adjacent bits in the diagnostic 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 registers are replaced with ’ACT818 diagnostic pipeline registers. The loop can be used to scan in a plete test routine starting point (Data, Address, etc.). Then after a specified number of machine cycles it scans out the results to be inspected for the expected results. WCS loading can be acplished 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. 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 m A n ’ACT818 has TTL-patible inputs n ’ACT818 is functionally- and pin-patible to AMD Am29818 and MMI 74S818 n Standard Microcircuit Drawing (SMD) 5962-9160901 Applications n n n n n n n n Register for microprogram control store Status register Data register Instruction register Interrupt mask register Pipeline register General purpose register Parallel-serial/serial-parallel converter Features n On-line and off-line system diagnostics Logic Symbol DS100251-3 TRI-STATE ® is a registered trademark of National Semiconductor Corporation. FACT™ is a trademark of Fairchild...