BL2

 

 

Burst Length

 

(CTEST5 bit 2)

BL1

BL0

Transfers

Dwords

 

 

 

 

 

0

0

0

2

4

 

 

 

 

 

0

0

1

4

8

 

 

 

 

 

0

1

0

8

16

 

 

 

 

 

0

1

1

16

321

1

0

0

32

641

1

0

1

64

1281

1

1

0

64

1281

1

1

1

Reserved

Reserved

 

 

 

 

 

1. The 944-byte FIFO must be enabled for these burst sizes.

SIOM

Source I/O Memory Enable

5

 

This bit is defined as an I/O Memory Enable bit for the

 

 

source address of a Memory Move or Block Move

 

 

Command. If this bit is set, then the source address is in

 

I/O space; and if cleared, then the source address is in

 

memory space.

 

 

This function is useful for register-to-memory operations

 

using the Memory Move instruction when the

 

 

LSI53C875A is I/O mapped. Bits 4 and 5 of the Chip Test

 

Two (CTEST2) register are used to determine the

 

 

configuration status of the LSI53C875A.

 

DIOM

Destination I/O Memory Enable

4

 

This bit is defined as an I/O Memory Enable bit for the

 

 

destination address of a Memory Move or Block Move

 

 

Command. If this bit is set, then the destination address

 

is in I/O space; and if cleared, then the destination

 

 

address is in memory space.

 

 

This function is useful for memory-to-register operations

 

using the Memory Move instruction when the

 

 

LSI53C875A is I/O mapped. Bits 4 and 5 of the Chip Test

 

Two (CTEST2) register are used to determine the

 

 

configuration status of the LSI53C875A.

 

ERLEnable Read Line3

This bit enables a PCI Read Line command. If this bit is set and the chip is about to execute a read cycle other than an opcode fetch, then the command is 0b1110.

SCSI Registers

4-67

Page 159
Image 159
LSI 53C875A technical manual Siom, Source I/O Memory Enable, Diom, Destination I/O Memory Enable, ERLEnable Read Line3