HTH[7:4],

Minimum Timeout

Minimum Timeout

SEL[3:0],

GEN[3:0]1

(40 MHz)

(50 MHz)

0110

4 ms

3.2 ms

 

 

 

0111

8 ms

6.4 ms

 

 

 

1000

16 ms

12.8 ms

 

 

 

1001

32 ms

25.6 ms

 

 

 

1010

64 ms

51.2 ms

 

 

 

1011

128 ms

102.4 ms

 

 

 

1100

256 ms

204.8 ms

 

 

 

1101

512 ms

409.6 ms

 

 

 

1110

1.024 s

819.2 ms

 

 

 

1111

2.048 s

1.6384 s

 

 

 

1.These values are correct if the CCF bits in the SCSI Control Three (SCNTL3) register are set according to the valid combinations in the bit description.

SELSelection Time-Out[3:0]

These bits select the SCSI selection/reselection time-out period. When this timing (plus the 200 μs selection abort time) is exceeded, the STO bit in the SCSI Interrupt Sta- tus One (SIST1) register is set. For a more detailed explanation of interrupts, refer to Chapter 2, “Functional Description.”

Register: 0x49 (0xC9)

SCSI Timer One (STIME1)

Read/Write

7

 

 

 

 

4

3

 

 

 

 

0

 

 

 

 

R

 

 

 

 

GEN[3:0]

 

 

x

 

x

 

x

x

0

 

0

 

0

0

 

 

 

 

 

 

 

 

 

 

 

 

 

R

 

Reserved

 

 

 

 

 

 

[7:4]

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

5-58

Operating Registers

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Image 132
LSI 53C810A technical manual Register 0x49 0xC9, SELSelection Time-Out30, Scsi Timer One STIME1 Read/Write