Register: 0x02 (0x82)

SCSI Control Two (SCNTL2)

Read/Write

7

6

 

 

 

 

 

 

 

0

SDU

 

 

 

 

R

 

 

 

0

x

 

x

x

x

 

x

x

x

SDU

 

SCSI Disconnect Unexpected

 

 

7

 

 

This bit is valid in the initiator mode only. When this bit is

 

 

set, the SCSI core is not expecting the SCSI bus to enter

 

 

the Bus Free phase. If it does, an unexpected disconnect

 

 

error is generated (see the Unexpected Disconnect bit in

 

 

the SCSI Interrupt Status Zero (SIST0) register, bit 2).

 

 

During normal SCRIPTS mode operation, this bit is set

 

 

automatically whenever the SCSI core is reselected, or

 

 

successfully selects another SCSI device. The SDU bit

 

 

should be cleared with a register write (move 0x07 and

 

 

SCNTL2 to SCNTL2) before the SCSI core expects a

 

 

disconnect to occur, normally prior to sending an Abort,

 

 

Abort Tag, Bus Device Reset, Clear Queue or Release

 

 

Recovery message, or before deasserting SACK/ after

 

 

receiving a Disconnect command or Command Complete

 

 

message.

 

 

 

 

 

 

R

 

Reserved

 

 

 

 

 

[6:0]

Register: 0x03 (0x83)

SCSI Control Three (SCNTL3)

Read/Write

7

 

6

 

 

4

3

2

 

0

R

 

 

 

SCF[2:0]

 

R

 

CCF[2:0]

 

0

 

0

 

0

0

x

0

0

0

R

 

Reserved

 

 

 

 

7

SCF[2:0]

 

Synchronous Clock Conversion Factor

[6:4]

 

 

 

These bits select the factor by which the frequency of

 

 

 

SCLK is divided before being presented to the

 

 

 

 

synchronous SCSI control logic. The bit encoding is

 

 

 

displayed in Table 5.1. For synchronous receive, the

 

 

 

output of this divider is always divided by 4 and that value

5-9

Page 83
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LSI 53C810A technical manual Register 0x02, Register 0x03, Sdu