Register: 0x57

Chip Control 1 (CCNTL1)

Read/Write

7

6

 

 

 

4

3

2

1

0

ZMODE

 

 

R

 

DDAC

64TIMOD

EN64TIBMV

EN64DBMV

0

x

 

x

 

x

0

0

0

0

ZMODE

 

High Impedance Mode

 

 

7

 

 

Setting this bit causes the LSI53C875A to place all output

 

 

and bidirectional pins except MAC/_TESTOUT, into a

 

 

high impedance state. Also, setting this bit causes all I/O

 

 

pins to become inputs, and all pull-ups and pull-downs to

 

 

be disabled. When this bit is set, the MAC/_TESTOUT

 

 

pin becomes the output pin for the connectivity test of the

 

 

LSI53C875A signals in the “AND-tree” test mode. In

 

 

order to read data out of the LSI53C875A, this bit must

 

 

be cleared. This bit is intended for board-level testing

 

 

only. Do not set this bit during normal system operation.

R

 

Reserved

 

 

 

 

[6:4]

DDAC

 

Disable Dual Address Cycle

 

3

When this bit is set, all 64-bit addressing as a master will be disabled. No dual address cycles will be generated by the LSI53C875A.

When this bit is cleared, the LSI53C875A will generate dual address cycles based on the master operation being performed and the value of its associated selector register.

64TIMOD

64-Bit Table Indirect Indexing Mode

2

 

When this bit is cleared, bits [24:28] of the first table entry

 

Dword will select one of 22 possible selectors to be used

 

in a BMOV operation. When this bit is set, bits [24:31] of

 

the first table entry Dword will be copied directly into

 

DNAD64 to provide 40-bit addressing capability. This bit

 

will only function if the EN64TIBMV bit is set.

 

Index Mode 0 (64TIMOD clear) table entry format:

 

[31:29]

[28:24]

[23:0]

 

 

 

 

 

Reserved

Sel Index

Byte Count

 

 

Source/Destination Address [31:0]

 

 

 

 

SCSI Registers

4-97

Page 189
Image 189
LSI 53C875A technical manual Zmode, Ddac, 64TIMOD