PSD501B1 datasheet(42/153 Pages) STMICROELECTRONICS

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PSD5XX Family

There are 5 programmable 8-bit I/O ports: Port A, Port B, Port C, Port D and Port E. These

ports all have multiple operating modes, depending on the configuration. Some of the basic

functions are providing input/output for the ZPLD, the Counter/Timer, or can be used for

standard I/O. Each port pin is individually configurable, thus enabling a single 8-bit port to

perform multiple functions. The I/O ports occupy 256 bytes of memory space as defined by

“CSIOP”. Refer to the System Configuration section for I/O register address offset.

To set up the port configuration the user is required to:

1. Define I/O port chip select (CSIOP) in the ABEL file.

2. Initialize certain port configuration registers in the user’s program and/or

3. Specify the configuration in the PSD5XX PSDsoft Software.

4. Unused input pins should be tied to VCC or GND.

The following is a description of the operating modes of the I/O ports. The functions of the

port registers are described in later sections.

9.3.1 Standard MCU I/O

The Standard MCU I/O Mode provides additional I/O capability to the microcontroller.

In this mode, the ports can perform standard I/O functions such as sensing or controlling

various external I/O devices. Operation options of this mode are as follows:

t Configuration

1. Declare pins or signals which are used as I/O in the ABEL file (PSDsoft).

2. Set the bit or bits in the Control Register to "1".

As Output Port

– Write output data to Data Out Register

– Set Direction Register to output mode

As Input Port

– Set Direction Register to input mode

– Read input from Data In Register

The port remains an output or input port as long as the Direction Register is not changed.

9.3.2 PLD I/O

The PLD I/O mode enables the port to be configured as an input to the ZPLD, or as an

output from the GPLD macrocell. The output can be tri-stated with a control signal defined

by a product term from the ZPLD. This mode is configured by the user in the PSD5XX

PSDsoft Software, and is enabled upon power up. For a detailed description, see the

section on the ZPLD.

t Configuration

1. Declare pins or signals in the ABEL file (PSDsoft)

2. Write logic equations in the ABEL file.

3. PSDcompiler maps the PLD function to the PSD.

9.3

I/O Ports

PSD501B1 Datasheet(PDF) 42 Page - STMicroelectronics