LSI 53C810A User Manual
Page 109
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ZMOD
High Impedance Mode
6
Setting this bit causes the LSI53C810A to place all output
and bidirectional pins into a high impedance state. In
order to read data out of the LSI53C810A, clear this bit.
This bit is intended for board-level testing only. Do not set
this bit during normal system operation.
ZSD
SCSI Data High Impedance
5
Setting this bit causes the LSI53C810A to place the SCSI
data bus SD[7:0] and the parity line (SDP) in a high
impedance state. In order to transfer data on the SCSI
bus, clear this bit.
SRTM
Shadow Register Test Mode
4
Setting this bit allows access to the shadow registers
used by Memory-to-Memory Move operations. When this
bit is set, register accesses to the
and
registers are directed to
the shadow copies STEMP (Shadow TEMP) and SDSA
(Shadow DSA). The registers are shadowed to prevent
them from being overwritten during a Memory-to-Memory
Move operation. The DSA and
registers contain the base address used for table indirect
calculations, and the address pointer for a call or return
instruction, respectively. This bit is intended for
manufacturing diagnostics only and should not be set
during normal operations.
MPEE
Master Parity Error Enable
3
Setting this bit enables parity checking during master
data phases. A parity error during a bus master read is
detected by the LSI53C810A. A parity error during a bus
master write is detected by the target, and the
LSI53C810A is informed of the error by the PERR/ pin
being asserted by the target. When this bit is cleared, the
LSI53C810A does not interrupt if a master parity error
occurs. This bit is cleared at power-up.