R

Reserved

2

EXT

Extend SREQ/SACK Filtering

1

 

LSI Logic TolerANT SCSI receiver technology includes a

 

special digital filter on the SREQ/ and SACK/ pins which

 

causes the disregarding of glitches on deasserting

 

 

edges. Setting this bit increases the filtering period from

 

30 ns to 60 ns on the deasserting edge of the SREQ/ and

 

SACK/ signals.

 

Note:

Never set this bit during fast SCSI (greater than

 

 

5 megatransfers per second) operations, because a valid

 

 

assertion could be treated as a glitch.

 

LOW

SCSI Low level Mode

0

 

Setting this bit places the LSI53C810A in low level mode.

 

In this mode, no DMA operations occur, and no SCRIPTS

 

execute. Arbitration and selection may be performed by

 

setting the start sequence bit as described in the SCSI

 

 

Control Zero (SCNTL0) register. SCSI bus transfers are

 

performed by manually asserting and polling SCSI

 

 

signals. Clearing this bit allows instructions to be

 

 

executed in SCSI SCRIPTS mode.

 

Note:

It is not necessary to set this bit for access to the SCSI

 

 

bit-level registers (SCSI Output Data Latch (SODL), SCSI

 

Bus Control Lines (SBCL), and input registers.

 

Register: 0x4F (0xCF)

SCSI Test Three (STEST3)

Read/Write

7

6

5

4

3

2

1

0

 

TE

STR

HSC

DSI

R

TTM

CSF

STW

 

0

0

0

0

x

0

0

0

 

 

 

 

 

 

 

 

 

TE

TolerANT Enable

 

 

 

7

Setting this bit enables the active negation portion of TolerANT technology. Active negation causes the SCSI Request, Acknowledge, Data, and Parity signals to be actively deasserted, instead of relying on external pull-ups, when the LSI53C810A is driving these signals. Active deassertion of these signals occurs only when the

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LSI 53C810A technical manual Register 0x4F 0xCF, Ext, Low