Registers: 0xD4–0xD7

Instruction Address (IA)

Read/Write

31

0

IA

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

IAInstruction Address[31:0]

This register always contains the address of the BMOV instruction that was executing when the phase mismatch occurred. This value will always match the value in the Entry Storage Address (ESA) except in the case of a table indirect BMOV in which case the ESA will have the address of the table indirect entry and this register will point to the address of the BMOV instruction.

Registers: 0xD8–0xDA

SCSI Byte Count (SBC)

Read Only

23

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

 

 

 

 

 

 

 

 

 

 

 

 

SBC

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SBC

 

 

SCSI Byte Count

 

 

 

 

 

 

 

 

[23:0]

This register contains the count of the number of bytes transferred to or from the SCSI bus during any given BMOV. This value is used in calculating the information placed into the Remaining Byte Count (RBC) and Updated Address (UA) register and should not need to be used in normal operations. There are two conditions in which this byte count will not match the number of bytes transferred exactly. If a BMOV is executed to transfer an odd number of bytes across a wide bus then the byte count at the end of the BMOV will be greater than the number of bytes sent by one. This will also happen in an odd byte count wide receive case. Also, in the case of a wide send in which there is a chain byte from a previous transfer, the count will not reflect the chain byte sent across the bus during that BMOV. The reason for this is due to the fact that to determine the correct address to start fetching data from after a phase mismatch this byte

Phase Mismatch Jump Registers

4-107

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Image 199
LSI 53C875A technical manual Registers 0xD4-0xD7, Registers 0xD8-0xDA, Sbc