G E N M o d u l e

Bits

Access

Mnemonic

Reset

Description

 

 

 

 

 

D07

R/W

CPUDIS

-ADDR26

CPU disable

 

 

 

 

0

CPU operational

 

 

 

 

1

CPU reset

 

 

 

 

Provides a mechanism to read back the bootstrap

 

 

 

 

value of ADDR26 (see "NS7520 bootstrap

 

 

 

 

initialization" on page 60). If this bit is set to 1, the

 

 

 

 

CPU is disabled.

 

 

 

 

 

D06

R/W

DMARST

0

DMA module reset

 

 

 

 

0

DMA module operational

 

 

 

 

1 DMA module (held in) reset

 

 

 

 

Provides a mechanism to issue a soft reset to the

 

 

 

 

DMA module without affecting any other

 

 

 

 

modules.

 

 

 

 

 

D05:04

R/W

BSYNC

0

TA_ input synchronizer

 

 

 

 

Defines the level of synchronization performed

 

 

 

 

within the NS7520 for TA_ input:

 

 

 

 

00

1-stage synchronizer

 

 

 

 

01

1-stage synchronizer

 

 

 

 

10

2-stage synchronizer

 

 

 

 

11 Do not use this setting

 

 

 

 

The NS7520 can process the TA_ input signal

 

 

 

 

using a 1-stage flip-flop synchronizer or a 2-stage

 

 

 

 

synchronizer. A 1- or 2-stage synchronizer must

 

 

 

 

be used when TA_ input is asynchronous to the

 

 

 

 

BCLK signal.

 

 

 

 

Note: The 2-stage synchronizer is preferable,

 

 

 

 

 

as it introduces one additional BCLK of

 

 

 

 

 

latency in the access cycle.

 

 

 

 

 

D03:00

N/A

Reserved

N/A

N/A

 

 

 

 

 

 

Table 24: System Control register bit definition

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Page 81
Image 81
Digi NS7520 manual CPU disable, DMA module reset, TA input synchronizer