LSI LSI53C896, Technical Manual

Page: 202 / 370

4-90 Registers
Note: To reset a timer before it expires and obtain repeatable
delays, the time value must be written to zero first, and then
written back to the desired value. This is also required
when changing from one time value to another.
HTH[7:4], SEL[3:0],
GEN[3:0]
1
Minimum Time-out
(40 or 160 MHz Clock)
2
HTHSF = 0,
GENSF = 0
HTHSF = 1,
GENSF = 1
0000 Disabled Disabled
0001 125
µ
s 2 ms
0010 250
µ
s 4 ms
0011 500
µ
s 8 ms
0100 1
µ
s 16 ms
0101 2 ms 32 ms
0110 4 ms 64 ms
0111 8 ms 128 ms
1000 16 ms 256 ms
1001 32 ms 512 ms
1010 64 ms 1 s
1011 128 ms 2 s
1100 256 ms 4.1 s
1101 512 ms 8.2 s
1110 1.024 s 16.4 s
1111 2.048 s 32.8 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. Ultra2 SCSI operation requires a quadrupled 40 MHz clock.
*