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PSD303R

Low Cost Field Programmable Microcontroller Peripherals

STMicroelectronics 

PSD3XX Family

Table 2.

PSD3XX Pin

Descriptions

Name

BHE/

PSEN

Type

Description

When the data bus is 8 bits:

This pin is for 8031 or compatible MCUs that use PSEN to

separate program space from data space. In this case, PSEN is

used for reads from the EPROM. Note: if your MCU does not

I output a PSEN signal, pull up this pin to VCC.

When the data bus is 16 bits:

This pin is BHE. When low, D8-D15 are read from or written to.

Note: in programming mode, this pin is pulsed between VPP and 0 V.

The following control signals can be connected to this port, based on

WR/VPP

or

your MCU (and the way you configure the PSD in PSDsoft):

I 1. WR—active-low write pulse.

R/W/VPP

2. R/W—active-high read/active-low write input.

Note: in programming mode, this pin must be tied to VPP.

t(s) The following control signals can be connected to this port, based on

c RD/E/DS

I

your MCU (and the way you configure the PSD in PSDsoft):

1. RD—active-low read input.

du 2. E—E clock input.

ro ) 3. DS—active-low data strobe input (3X2/3X3 devices only)

- Obsolettee PProduct(s A19/CSI

The following control signals can be connected to this port:

1. CSI—Active-low chip select input. If your MCU supports a chip

select output, and you want the PSD to save power when not

I

selected, use this pin as a chip select input.

2. If you don’t wish to use the CSI feature, you may use this pin as

an additional input (logic or address) to the PAD. A19 can be

latched (with ALE/AS), or a transparent logic input.

) le PSD3XX/ZPSD3XX:

t(s o This pin is user-programmable and can be configured to reset on a

s high- or low-level input. Reset must be applied for at least 100 ns.

Product(s) - Ob Reset

I ZPSD3XXV:

This pin is not configurable, and the chip will only reset on an

active-low level input. Reset must be applied for at least 500 ns,

and no operations may take place for an additional 500 ns minimum.

(See Figure 8.)

Obssoolleettee Produc ALE/AS

If you use an MCU that has a multiplexed bus:

Connect ALE or AS to this pin. The polarity of this pin is configurable.

The trailing edge of ALE/AS latches all multiplexed address inputs

(and BHE where applicable).

I If you use an MCU that does not have a multiplexed bus:

If your MCU uses ALE/AS, connect the signal to this pin.

Otherwise, use this pin for a generic logic input to the PAD.

(Non-3X1 devices only.)

Ob These pins make up Port A. These port pins are configurable, and

PA0

can have the following functions: (see Figure 5A and 5B)

PA1

1. Track AD7-AD0. This feature repeats the MCU address and data

PA2

I/O

bus on all Port A pins.

PA3

2. MCU I/O—in this mode, the direction of the pin is defined by its

PA4

direction bit, which resides in the direction register.

PA5

3. Latched address output.

PA6

4. CMOS or open-drain output.

PA7

5. If your MCU is non-multiplexed: data bus input—connect your

data bus (D0-7) to these pins. See Figure 3.

Legend: The Type column abbreviations are: I = input only; I/O = input/output; P = power.

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