Z8F021ASH020SC datasheet(62/276 Pages) ZILOG

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PS022815-0206

General-Purpose I/O

Z8 Encore! XP® 4K Series

Product Specification

functions as GPIO. If enabled, select one of four alternate functions using alternate func-

tion set subregisters 1 and 2 as described in the Port A–D Alternate Function Set 1 Sub-

Registers on page 45 and Port A–D Alternate Function Set 2 Sub-Registers on page 46.

Refer

to the GPIO Alternate Functions on page 33 to determine the alternate function asso-

ciated with each port pin.

Do not enable alternate functions for GPIO port pins for which there is no

associated alternate function. Failure to follow this guideline can result in

unpredictable operation.

AF[7:0]—Port Alternate Function enabled

0 = The port pin is in normal mode and the DDx bit in the Port A–D Data Direction sub-

1 = The alternate function selected through Alternate Function Set sub-registers is

enabled. Port pin operation is controlled by the alternate function.

Port A–D Output Control Sub-Registers

The Port A–D Output Control sub-register (Table 22) is accessed through the Port A–D

Control register by writing 03H to the Port A–D Address register. Setting the bits in the

Port A–D Output Control sub-registers to 1 configures the specified port pins for open-

drain operation. These sub-registers affect the pins directly and, as a result, alternate func-

tions are also affected.

POC[7:0]—Port Output Control

These bits function independently of the alternate function bit and always disable the

Table 21. Port A–D Alternate Function Sub-Registers (PxAF)

BITS

FIELD

AF7

AF6

AF5

AF4

AF3

AF2

AF1

AF0

RESET

00H (Ports A–C); 01H (Port D); 04H (Port A of 8-pin device)

R/W

ADDR

If 02H in Port A–D Address Register, accessible through the Port A–D Control Register

Table 22. Port A–D Output Control Sub-Registers (PxOC)

BITS

FIELD

POC7

POC6

POC5

POC4

POC3

POC2

POC1

POC0

RESET

000

R/W

R/WR/W

ADDR

If 03H in Port A–D Address Register, accessible through the Port A–D Control Register

Caution:

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