ST6391 datasheet(30/68 Pages) STMICROELECTRONICS

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PA7-PA0. These are the I/O port A data bits. Reset

at power-on.

PB7-PB0. These are the I/O port B data bits. Reset

at power-on.

PC7-PC0. Set to 04h at power-on. Bit 2 (PC2 pin)

is set to one (open drain therefore high im-

pedence).

PA7-PA0. These are the I/O port A data direction

bits. When a bit is cleared to zero the related I/O

line is in input mode, if bit is set to one the related

I/O line is in output mode. Reset at power-on.

PB7-PB0. These are the I/O port B data direction

bits. When a bit is cleared to zero the related I/O

line is in input mode, if bit is set to one the related

I/O line is in output mode. Reset at power-on.

PC7-PC0. These are the I/O port C data direction

bits. When a bit is cleared to zero the related I/O

line is in input mode, if bit is set to one the related

I/O line is in output mode. Set to 04h at power-on.

Bit 2 (PC2 pin) is set to one (output mode se-

lected).

DDR

Mode

Option

Input

With on-chip pull-up

resistor

Input

Without on-chip pull-up resistor

Output

Open-drain or Push-Pull

Note: X: Means don’t care.

Table 8. I/O Port Options Selection

DRA, DRB, DRC

Port A, B, C Data Register

( C0h PA, C1h PB, C2h PC Read/ Write )

D7 D6 D5 D4 D3 D2 D1 D0

A0 - PA7 = Data Bits

PB0 - PB7 = Data Bits

PC0 - PC7 = Data Bits

Figure 28. Port A, B, C Data Register

DDRA, DDRB,DDRC

Port A, B, C Data Direction Register

( C4h PA, C5h PB, C6h PC Read/ Write )

D7 D6 D5 D4 D3 D2 D1 D0

PA0 - PA7 = Data Direction Bits

PB0 - PB7 = Data Direction Bits

PC0 - PC7 = Data Direction Bits

“0” Defines bit as Inpu t

”1” Defines bit as Outpu t

Figure 29. Port A, B, C Data Register

I/O Pin Programming

Each pin can be individually programmed as input or

output with different input and output configurations.

This is achieved by writing to the relevant bit in the

data (DR) and data direction register (DDR). Table

8 shows all the port configurations that can be se-

lected by the user software.

INPUT/OUTPUT PORTS (Continued)

ST6391,92,93,95,97,99

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