FE

Fetch Enable

6

 

The internal opcode fetch signal is presented on GPIO0

 

if this bit is set, regardless of the state of bit 0

 

 

(GPIO0_EN).

 

R

Reserved

5

GPIO_EN[1:0] GPIO Enable

[1:0]

 

These bits power up set, causing the GPIO1 and GPIO0

 

pins to become inputs. Resetting these bits causes

 

 

GPIO[1:0] to become outputs.

 

Register: 0x48 (0xC8)

SCSI Timer Zero (STIME0)

Read/Write

7

 

 

 

 

 

4

3

 

 

 

 

 

 

0

 

 

 

HTH[3:0]

 

 

 

 

SEL[3:0]

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0

0

 

 

0

 

0

 

0

 

0

 

 

0

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HTH[3:0]

 

 

Handshake-to-Handshake Timer Period

 

 

[7:4]

 

 

 

 

These bits select the handshake-to-handshake time-out

 

 

 

 

period, the maximum time between SCSI handshakes

 

 

 

 

(SREQ/ to SREQ/ in target mode, or SACK/ to SACK/ in

 

 

 

 

initiator mode). When this timing is exceeded, an interrupt

 

 

 

 

is generated and the HTH bit in the SCSI Interrupt Status

 

 

 

 

One (SIST1) register is set. The following table contains

 

 

 

 

time-out periods for the Handshake-to-Handshake Timer,

 

 

 

 

the Selection/Reselection Timer (bits [3:0]), and the

 

 

 

 

 

General Purpose Timer (SCSI Timer One (STIME1) bits

 

 

 

 

[3:0]). For a more detailed explanation of interrupts, refer

 

 

 

 

to Chapter 2, “Functional Description.”

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

HTH[7:4],

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SEL[3:0],

 

Minimum Timeout

Minimum Timeout

 

 

 

 

 

GEN[3:0]1

 

 

(40 MHz)

 

 

 

(50 MHz)

 

 

 

 

 

0000

 

 

 

Disabled

 

 

 

Disabled

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0001

 

 

 

125 μs

 

 

 

100 μs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0010

 

 

 

250 μs

 

 

 

200 μs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0011

 

 

 

500 μs

 

 

 

400 μs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0100

 

 

 

1 ms

 

 

 

800 μs

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0101

 

 

 

2 ms

 

 

 

1.6 ms

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5-57

Page 131
Image 131
LSI 53C810A Register 0x48 0xC8, GPIO0EN, Scsi Timer Zero STIME0 Read/Write, HTH30 Handshake-to-Handshake Timer Period