13.2PIO MODE REGISTERS

Table 13-2shows the possible settings for the PIO Mode and PIO Direction bits. The Am186ER and Am188ER microcontrollers default the 32 PIO pins to either 00b (normal operation) or 01b (PIO input with weak internal pullup or pulldown enabled).

Pins that default to active High outputs at reset are pulled down. All other pins are pulled up or are normal operation. See Table 13-2.The column titled Power-On Reset Status in Table 13-1lists the defaults for the PIOs.

The internal pullup resistor has a value of approximately 100 kohms. The internal pulldown resistor has a value of approximately 100 kohms.

Table 13-2 PIO Mode and PIO Direction Settings

 

 

 

 

 

 

 

PIO Mode

PIO Direction

Pin Function

 

 

 

 

 

 

 

0

0

Normal operation

 

 

 

 

 

 

 

0

1

PIO input with pullup/pulldown

 

 

 

 

 

 

 

1

0

PIO output

 

 

 

 

 

 

 

1

1

PIO input without pullup/pulldown

 

 

 

 

 

 

 

 

 

 

 

Figure 13-2 PIO Mode 1 Register

 

Figure 13-3 PIO Mode 0 Register

 

 

(PIOMODE1, offset 76h)

 

 

(PIOMODE0, offset 70h)

 

15

7

0

15

7

0

PMODE (31–16)

PMODE (15–0)

13.2.1PIO Mode 1 Register (PIOMODE1, Offset 76h)

The value of PIOMODE1 at reset is 0000h.

Bits 15–0: PIO Mode Bits (PMODE31–PMODE16) —This field with the PIO direction registers determines whether each PIO pin performs its pre-assigned function or is enabled as a custom PIO signal. The most significant bit of the PMODE field determines whether PIO31 is enabled, the next bit determines whether PIO30 is enabled, and so on.

Table 13-2shows the values that the PIO mode bits and the PIO direction bits can encode.

13.2.2PIO Mode 0 Register (PIOMODE0, Offset 70h)

The value of PIOMODE0 at reset is 0000h.

Bits 15–0: PIO Mode Bits (PMODE15–PMODE0) —This field is a continuation of the PMODE field in the PIO Mode 1 register.

Programmable I/O Pins

13-3

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Image 167
AMD Am188TMER PIO Mode Registers, PIO Mode 1 Register PIOMODE1, Offset 76h, PIO Mode 0 Register PIOMODE0, Offset 70h