Z89321 datasheet(23/40 Pages) ZILOG

23 / 40 page

Z89321/371/391

Zilog

16-Bit Digital Signal Processors

DS97DSP0100

P R E L I M I N A R Y

PERIPHERAL OPERATION

Disabling Peripherals

Disabling a peripheral (CODEC Interface, Counter) allows

general-purpose use of the EXT address for the disabled

peripheral. If the peripheral is not disabled, the EXT control

signals and EXT data are still provided, but transfer of data

on the EXT pins is not available (because internal transfers

are being processed on the internal bus). Care must be

taken to ensure that control of the EXT bus does not cause

bus conflicts.

Reading Data from CODEC Interface*

External data is serially transferred into the CODEC inter-

face registers from an external CODEC. This serial data is

loaded into EXT5-2 (8- or 16-bit modes). Because the in-

terface is double-buffered, data must be transferred to

EXT5-1 before being transferred along the internal data

bus of the processor. This is accomplished by writing data

to EXT5-2.

Writing Data to CODEC Interface

Internal data is transferred from the internal data bus of the

processor to the EXT5-2 register. The CODEC interface

constantly transfers and receives data during normal oper-

ation. Data to be transferred is loaded to EXT5-2 and is au-

tomatically serially transferred.

Note: EXT5-1 and EXT5-2 are used in the example, but

this information applies equally to EXT6-1 and EXT6-2.

(Refer to Figure 20, CODEC Block Diagram.)

LOADING EXT7

Because EXT7 is double-buffered, a pair of writes are per-

formed when loading the EXT7 registers (Figure 19).

Interrupts

The Z89321 features three interrupts:

If all peripherals are enabled, INT0 (general-purpose) can

be used.

Figure 19. EXT7 Register ConÞguration

Internal 16-Bit Bus

Wait-State Register

EXT7-1

EXT7-2

CODEC Timer Register

EXT7-1

EXT7-2

LD EXT7, #%54F4

Loads CODEC Timer Register

LD EXT7, #%6CDA

Loads Wait-State Register

LD @P0:0, EXT7

Reads EXT7-1 and places

data in RAM

INT0

General-Purpose

INT1

CODEC Interface

INT2

13-Bit Timer

Z89321 Datasheet(PDF) 23 Page - Zilog, Inc.

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