Z8 Encore! XP® F08xA Series
Product Specification
39
Table 18. Port A–D Data Direction Sub-Registers (PxDD)
BITS
7
6
5
4
3
2
1
0
DD7
DD6
DD5
DD4
DD3
DD2
DD1
DD0
FIELD
RESET
R/W
1
1
1
1
1
1
1
1
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
If 01H in Port A–D Address Register, accessible through the Port A–D Control Register
ADDR
DD[7:0]—Data Direction
These bits control the direction of the associated port pin. Port Alternate Function opera-
tion overrides the Data Direction register setting.
0 = Output. Data in the Port A–D Output Data register is driven onto the port pin.
1 = Input. The port pin is sampled and the value written into the Port A–D Input Data Reg-
ister. The output driver is tristated.
Port A–D Alternate Function Sub-Registers
The Port A–D Alternate Function sub-register (Table 19) is accessed through the Port A–
D Control register by writing 02Hto the Port A–D Address register. The Port A–D Alter-
nate Function sub-registers enable the alternate function selection on pins. If disabled, pins
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 42 and “Port A–D Alternate Function Set 2 Sub-Registers” on page 42.
Refer to the “GPIO Alternate Functions” on page 32 to determine the alternate function asso-
ciated with each port pin.
Caution:
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.
Table 19. Port A–D Alternate Function Sub-Registers (PxAF)
BITS
7
6
5
4
3
2
1
0
AF7
AF6
AF5
AF4
AF3
AF2
AF1
AF0
FIELD
RESET
R/W
00H (Ports A–C); 01H (Port D)
R/W
If 02H in Port A–D Address Register, accessible through the Port A–D Control Register
ADDR
AF[7:0]—Port Alternate Function enabled
0 = The port pin is in normal mode and the DDxbit in the Port A–D Data Direction sub-
register determines the direction of the pin.
PS024705-0405
P R E L I M I N A R Y
General-Purpose I/O
ZILOG [ ZILOG, INC. ]
