PSD501B1 datasheet(43/153 Pages) STMICROELECTRONICS

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PSD5XX Family

9.3.3 Address Out

For microcontrollers with a multiplexed address/data bus, the I/O ports in Address-Out

mode are able to provide latched address outputs (A0 – A15) to external devices. This

mode of operation requires the user to:

t Configuration

1. Declare the pins used as address line outputs in the ABEL file PSDsoft.

2. Write “0” to the corresponding bit in the Control Register associated

with each I/O port.

3. Set the Direction Register to Output Mode.

9.3.4 Address In

1. For Port A – as other address line (A2 – A7 and A16 – A23) inputs to the DPLD.

Additional address inputs included in the EPROM decoding must come from Port A.

The address inputs are latched internally by ALE/AS if Multiplexed Bus is specified in

PSDsoft.

2. For Ports C and D – as adress inputs to the ZPLD for general decoding, should not be

used in EPROM decoding.

t Configuration

1. Declare pins or signals used as Address In in the ABEL file (PSDsoft).

2. Write latch equations in the ABL file, e.g., A16.LE = ALE

3. Include latched address in logic equations.

9.3.5 Data Port

In this mode, the port is acting as a data bus port for a microcontroller which has a

non-multiplexed address/data bus. In this configuration, the Data Port is connected to the

data bus of the microcontroller and the ADIO port is connected to the address bus.

t Configuration

Select the non-multiplexed bus option in PSD configuration (PSDsoft).

9.3.6 Special Function Out

This mode is per-pin configurable. When enabled, the special function assigned to the

particular pin is driven out. Special functions consist of Timer and Interrupt outputs.

t Configuration

1. Specify the output function in the PSD configuration (PSDsoft).

2. PSD compiler assigns pins for the selected function.

3. Write “1” to the corresponding bit in the Special Function Register.

I/O Ports

(Cont.)

PSD501B1 Datasheet(PDF) 43 Page - STMicroelectronics