ERMP

Enable Read Multiple

2

 

If this bit is set and cache mode is enabled, a Read

 

 

Multiple command is used on all read cycles when it is

 

 

legal.

 

BOF

Burst Opcode Fetch Enable

1

 

Setting this bit causes the LSI53C875A to fetch

 

 

instructions in burst mode. Specifically, the chip bursts in

 

the first two Dwords of all instructions using a single bus

 

ownership. If the instruction is a Memory-to-Memory

 

 

Move type, the third Dword is accessed in a subsequent

 

bus ownership. If the instruction is an indirect type, the

 

 

additional Dword is accessed in a subsequent bus

 

 

ownership. If the instruction is a table indirect block move

 

type, the chip accesses the remaining two Dwords in a

 

 

subsequent bus ownership, thereby fetching the four

 

 

Dwords required in two bursts of two Dwords each. If

 

 

prefetch is enabled, this bit has no effect. This bit also

 

 

has no effect on fetches out of SCRIPTS RAM.

 

MANManual Start Mode0

Setting this bit prevents the LSI53C875A from automatically fetching and executing SCSI SCRIPTS when the DMA SCRIPTS Pointer (DSP) register is written. When this bit is set, the Start DMA bit in the DMA Control (DCNTL) register must be set to begin SCRIPTS execution. Clearing this bit causes the LSI53C875A to automatically begin fetching and executing SCSI SCRIPTS when the DSP register is written. This bit normally is not used for SCSI SCRIPTS operations.

4-68Registers

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LSI 53C875A technical manual Ermp, Enable Read Multiple, Bof, Burst Opcode Fetch Enable, MANManual Start Mode0