Register: 0x05

SCSI Transfer (SXFER)

Read/Write

7

 

5

4

 

 

 

0

 

TP[2:0]

 

 

 

MO[4:0]

 

 

 

 

 

 

 

 

 

 

0

0

0

0

0

0

0

0

 

 

 

 

 

 

 

 

Note: When using Table Indirect I/O commands, bits [7:0] of this register are loaded from the I/O data structure.

TP[2:0]

SCSI Synchronous Transfer Period

[7:5]

 

These bits determine the SCSI synchronous transfer

 

period used by the LSI53C875A when sending

 

 

synchronous SCSI data in either the initiator or target

 

mode. These bits control the programmable dividers in

 

the chip.

 

 

 

 

 

 

 

 

 

 

 

 

 

TP2

TP1

TP0

XFERP

 

 

 

 

 

 

 

 

 

 

0

0

0

4

 

 

 

 

 

 

 

 

 

 

0

0

1

5

 

 

 

 

 

 

 

 

 

 

0

1

0

6

 

 

 

 

 

 

 

 

 

 

0

1

1

7

 

 

 

 

 

 

 

 

 

 

1

0

0

8

 

 

 

 

 

 

 

 

 

 

1

0

1

9

 

 

 

 

 

 

 

 

 

 

1

1

0

10

 

 

 

 

 

 

 

 

 

 

1

1

1

11

 

 

 

 

 

 

 

 

 

The synchronous transfer period the LSI53C875A should use when transferring SCSI data is determined in the following example:

The LSI53C875A is connected to a hard disk which can transfer data at 10 Mbytes/s synchronously. The LSI53C875A’s SCLK is running at 40 MHz. The synchronous transfer period (SCSI Transfer (SXFER)) is found as follows:

SXFERP = Period/SSCP + ExtCC

Period = 1 Frequency = 1 10 Mbytes/s = 100 ns

SSCP = 1 SSCF = 1 40 MHz = 25 ns

SCSI Registers

4-31

Page 123
Image 123
LSI 53C875A technical manual Scsi Transfer Sxfer Read/Write, TP20 Scsi Synchronous Transfer Period