~ National ~ Semiconductor - Al Kossow's Bitsavers

8.0 Remote Interface and Arbitration System (Continued)
IA
ADDR
INSTR
I DATA RAM
iWR
READ
OE
WRITE
WR
BCP A ADDR DATA
ALE
...1L
RAM
AD
ill I--
WR-PEND XACK Ff1
REM-RD REM-WR CMD ill ~
~
Wi<
~ DATA
~ DECODE CONTROL ., 4Y~ ~ I
=='
READ WRITE WAIT +--
REMOTE
PROCESSOR
DATA
ADDR
FIGURE 14. BCP/Remote Processor Interface
TABLE XXV. RIAS Inputs and Outputs
TLlF/9336-19
Signal InlOut Pin
Reset
State
Function
CMD In 45 X CoMmanD input. When high, remote accesses are directed to the
Remote Interface Configuration register, (RIC). When low, remote
accesses are directed to Data Memory, Instruction Memory or the
Program Counter as determined by (RIC).
LCL Out 31 0 loCal. Normally low, goes high when the BCP relinquishes the data
and address bus to service a remote access.
LOCK In 44 X Setting this input high will lOCK out local (BCP) accesses to Data
Memory. Once the remote processor has been granted the bus,
LOCK gives it sole access to the bus and BCP accesses are
"waited".
RAE In 46 X Remote Access Enable. Setting this input low allows host access of
BCP functions and memory.
REM-RD In 47 X REMote ReaD. When low along with RAE, a remote read cycle is
requested; serviced by the BCP when the data bus becomes
available.
REM-WR In 48 X REMote WRite. When low along with RAE, a remote write cycle is
requested; serviced by the BCP when the data bus becomes
available.
WR-PEND Out 49 1 WRite PENDing. In a system configuration where remote write
cycles are latched, WR-PEND will go low, indicating that the latches
contain valid data which have yet to be serviced by the BCP.
XACK Out 50 1 Transfer ACKnowledge. Normally high, goes low on REM-RD or
REM-WR going low (if RAE low) returning high when the transfer is
complete. Normally used as a "wait" Signal to a remote processor.
(In the Latched Write mode, XACK will only transition if a second
remote access begins before the first one completes.)
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