LSI 53C875A User Manual
4-32
Registers
(This SCSI synchronous core clock is determined in
SCNTL3 bits [6:4], ExtCC = 1 if SCNTL1 bit 7 is asserted
and the LSI53C875A is sending data. ExtCC = 0 if the
LSI53C875A is receiving data.)
SCNTL3 bits [6:4], ExtCC = 1 if SCNTL1 bit 7 is asserted
and the LSI53C875A is sending data. ExtCC = 0 if the
LSI53C875A is receiving data.)
SXFERP = 100
÷
25 = 4
Where:
shows examples of synchronous transfer periods and rates for
SCSI-1.
SXFERP
Synchronous transfer period.
SSCP
SCSI synchronous core period.
SSCF
SCSI synchronous core frequency.
ExtCC
Extra clock cycle of data setup.
Table 4.3
Examples of Synchronous Transfer Periods and Rates
for SCSI-1
for SCSI-1
CLK (MHz)
SCSI CLK
÷
SCNTL3
Bits [6:4]
XFERP
(SXFER
Bits [7:5])
Synch.
Transfer
Period (ns)
Synch.
Transfer Rate
(Mbytes/s)
66.67
3
4
180
5.55
66.67
3
5
225
4.44
50
2
4
160
6.25
50
2
5
200
5
40
2
4
200
5
37.50
1.5
4
160
6.25
33.33
1.5
4
180
5.55
25
1
4
160
6.25
20
1
4
200
5
16.67
1
4
240
4.17