Scsi Error Status Register; General Purpose Inputs Register - Motorola MVME172 Programmer's Reference Manual

SCSI Error Status Register

ADR/SIZ
BIT
31
NAME
OPER
R
RESET 0
SCLR
LTO, EXT, PRTY

General Purpose Inputs Register

The contents of a PAL and the state of an 8-position jumper block are
translated to bit settings of the General Purpose Inputs Register, Version
Register and DRAM/SRAM Options Register when the MC2 chip is reset.
These registers are read only. Writes to these registers are terminated
without exception but do not change their contents.
http://www.mcg.mot.com/literature
$FFF4202C (8 bits)
30 29 28
R R R
0 0 0
Writing a 1 to this bit clears bits LTO, EXT, and PRTY.
Reading this bit always yields 0.
These bits indicate the status of the last local bus error
condition encountered by the SCSI processor while
performing DMA accesses to the local bus. A local bus
error condition is flagged by the assertion of TEA*. When
the SCSI processor receives TEA*, if the source of the
error is local time-out, then LTO is set and EXT and
PRTY are cleared. If the source of the TEA* is due to an
error in going to the VMEbus, then EXT is set and the
other two status bits are cleared. If the source of the error
is DRAM parity check error, then PRTY is set and the
other two status bits are cleared. If the source of the error
is none of the above conditions, then all three bits are
cleared. Writing a 1 to bit 24 (SCLR) also clears all three
bits.
Programming Model
27 26 25
PRTY EXT LTO
R R R
0 PL 0 PL 0 PL
3
24
SCLR
R
0 PL
3-33