LSI LSI53C896, Technical Manual

Page: 201 / 370

SCSI Registers 4-89
HTHSF Handshake-to-Handshake Timer Scale Factor 4
Setting this bit causes this timer to shift by a factor of 16.
Refer to the
SCSI Timer Zero (STIME0) register
description for details.
GEN[3:0] General Purpose Timer Period [3:0]
These bits select the period of the general purpose timer.
The time measured is the time between enabling and
disabling of the timer. When this timing is exceeded, the
GEN bit in the
SCSI Interrupt Status One (SIST1) register
is set. Refer to the table under SCSI Timer Zero
(STIME0) , bits [3:0], for the available time-out periods.
HTH[7:4], SEL[3:0],
GEN[3:0]
1
Minimum Time-out
(50 MHz Clock)
2
HTHSF = 0,
GENSF = 0
HTHSF = 1,
GENSF = 1
0000 Disabled Disabled
0001 100
µ
s 1.6 ms
0010 200
µ
s 3.2 ms
0011 400
µ
s 6.4 ms
0100 800
µ
s 12.8 ms
0101 1.6 ms 25.6 ms
0110 3.2 ms 51.2 ms
0111 6.4 ms 102.4 ms
1000 12.8 ms 204.8 ms
1001 25.6 ms 409.6 ms
1010 51.2 ms 819.2 ms
1011 102.4 ms 1.6 s
1100 204.8 ms 3.2 s
1101 409.6 ms 6.4 s
1110 819.2 ms 12.8 s
1111 1.6 s 25.6 s
1. These values will be correct if the CCF bits in the SCSI
Control Three (SCNTL3) register are set according to the
valid combinations in the bit description.
2. 50 MHz clock is not supported for Ultra2 SCSI operation.
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