UPSD3422 datasheet(69/293 Pages) STMICROELECTRONICS

69 / 293 page

uPSD34xx

I/O ports of mcu module

69/293

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

(~150K ohms) to VCC.

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

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 uPSD34xx devices) are dedicated to bring out

the 8032 MCU address, data, and control signals to external pins. One 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 the eight upper address signals do not come out to pins

on the port. If high-order address signals are required on external pins (MCU addresses

A[15:8]), 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 PSD Module section,

“Section 28.5.39: Latched address output mode on page 232 for details.

Figure 16 on page 71 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 17 on page 71

through Figure 19 on page 72).

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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