UPSD3312D datasheet(76/272 Pages) STMICROELECTRONICS

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I/O ports of MCU module

UPSD33xx

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Doc ID 9685 Rev 7

I/O ports of MCU module

The MCU module has three 8-bit I/O ports: Port 1, Port 3, and Port 4. The PSD module has

four other I/O ports: Port A, B, C, and D. This section describes only the I/O ports on the

MCU module.

I/O ports will function as bi-directional General Purpose I/O (GPIO), but the port pins can

have alternate functions assigned at run-time by writing to specific SFRs. The default

operating mode (during and after reset) for all three ports is GPIO input mode. Port pins that

have no external connection will not float because each pin has an internal weak pull-up

(~150 kOhms) to VCC.

I/O ports 3 and 4 are 5 V tolerant, meaning they can be driven/pulled externally up to 5.5 V

without damage. The pins on Port 4 have a higher current capability than the pins on Ports 1

and 3.

Three additional MCU ports (only on 80-pin UPSD33xx devices) are dedicated to bring out

the 8032 MCU address, data, and control signals to external pins. One port, named

MCUA[11:8], contains four MCU address signal outputs. Another port, named MCUAD[7:0],

has eight multiplexed address/data bidirectional signals. The third port has MCU bus control

outputs: read, write, program fetch, and address latch. These ports are typically used to

connect external parallel peripherals and memory devices, but they may NOT be used as

GPIO. Notice that only four of the eight upper address signals come out to pins on the port

MCUA[11:8]. If additional high-order address signals are required on external pins (MCU

addresses A[15:12]), then these address signals can be brought out as needed to PLD

output pins or to the Address Out mode pins on PSD module ports. See Section 27.4.39:

Latched address output mode on page 214 for details.

Figure 15 on page 78 represents the flexibility of pin function routing controlled by the SFRs.

Each of the 24 pins on three ports, P1, P3, and P4, may be individually routed on a pin-by-

pin basis to a desired function.

17.1

MCU port operating modes

MCU port pins can operate as GPIO or as alternate functions (see Figure 16 through

Figure 18 on page 80).

Depending on the selected pin function, a particular pin operating mode will automatically

be used:

●

GPIO - quasi-bidirectional mode

●

UART0, UART1 - quasi-bidirectional mode

●

SPI - quasi-bidirectional mode

●

I2C - open drain mode

●

ADC - analog input mode

●

PCA output - push-pull mode

●

PCA input - input only (quasi-bidirectional)

●

Timer 0,1,2 - input only (quasi-bidirectional)

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