field, see the definition for SCSI Status One (SSTAT1) bits [7:4].

SPL1

Latched SCSI Parity for SD[15:8]

3

 

This active HIGH bit reflects the SCSI odd parity signal

 

 

corresponding to the data latched into the most

 

 

significant byte in the SCSI Input Data Latch (SIDL)

 

 

register.

 

R

Reserved

2

LDSC

Last Disconnect

1

 

This bit is used in conjunction with the Connected (CON)

 

bit in SCSI Control One (SCNTL1). It allows the user to

 

detect the case in which a target device disconnects, and

 

then some SCSI device selects or reselects the

 

 

LSI53C875A. If the Connected bit is asserted and the

 

 

LDSC bit is asserted, a disconnect is indicated. This bit

 

is set when the Connected bit in SCNTL1 is off. This bit

 

is cleared when a Block Move instruction is executed

 

 

while the Connected bit in SCNTL1 is on.

 

SDP1

SCSI SDP1 Signal

0

 

This bit represents the active HIGH current state of the

 

SCSI SDP1 parity signal. It is unlatched and may change as it is read.

Registers: 0x10–0x13

Data Structure Address (DSA)

Read/Write

31

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DSA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

0

0

0

0

0

0

0

0

0

 

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

DSA

 

 

 

Data Structure Address

 

 

 

 

 

 

 

 

 

[31:0]

This 32-bit register contains the base address used for all table indirect calculations. The DSA register is usually loaded prior to starting an I/O, but it is possible for a SCRIPTS Memory Move to load the DSA during the I/O.

During any Memory-to-Memory Move operation, the contents of this register are preserved. The power-up value of this register is indeterminate.

SCSI Registers

4-47

Page 139
Image 139
LSI 53C875A technical manual SPL1, Ldsc, SDP1, Dsa