PSD211R datasheet(20/51 Pages) STMICROELECTRONICS

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PSD211R Family

12.0

Control Signals

(Cont.)

12.1 ALE or AS

Connect the ALE or AS signal from your MCU to this pin where applicable, and program

the polarity using PSDsoft. The trailing edge (when the signal goes inactive) of ALE or AS

latches the address on the appropriate address pins.

12.2 WR or R/W

Your MCU should output a stand-alone write signal (WR) or a multiplexed read/write signal

(R/W). In either case, the signal should be connected to this pin.

12.3 RD/E

Your MCU should output either RD or E (clock). In either case, connect the appropriate

signal to this pin. Note: if you have an MCU that outputs DS, it will not be compatible with

the PSD211R, and you must use a PSD3XX family device.

12.4 PSEN

t If your MCU does not output PSEN (or some program select enable equivalent signal),

tie this pin to Vcc (through a series resistor), and skip to the next signal.

t If you use an 8-bit 8031 compatible MCU that outputs a separate signal when

accessing program space, such as PSEN, connect it to this pin. You would then use

PSDsoft to configure the EPROM in the PSD211R to respond to PSEN only or PSEN

and RD. If you have an 8031 compatible MCU, refer to the “Program/Data Space and

the 8031” section for further information.

12.5 A19/CSI

This pin is configured using PSDsoft to be either a chip select for the entire PSD device or

an additional PAD input. If your MCU can generate a chip-select signal, and you wish to

save power, use the PSD chip select feature. Otherwise, use this pin as an address or logic

input.

t When configured as CSI (active-low PSD chip select): a low on this pin keeps the

PSD in normal operation. However, when a high is detected on the pin, the PSD

enters Power-down Mode. See Tables 7A and 7B for information on signal states

during Power-down Mode. See section 16 for details about the reduction of power

consumption.

t When configured as A19, the pin can be used as an additional input to the PADs.

It can be used for address or logic. It can also be ALE/AS dependent or a transparent

input, which is determined by your PSDsoft design file. In A19 mode, the PSD is

always enabled.

Port

Configuration Mode(s)

State

AD0–AD15

All

Input (Hi-Z)

Port Pins PA0–PA7

MCU I/O

Unchanged

Latched Address Out

Logic 1

MCU I/O

Unchanged

Port Pins PB0–PB7

Chip Select Outputs, CS0–CS7, CMOS

Logic 1

Chip Select Outputs, CS0–CS7, Open Drain

Hi-Z

Port Pins PC0–PC2

Address or Logic Inputs, A16-A18

Input (Hi-Z)

Chip Select Outputs, CS8–CS10, CMOS only

Logic 1

Table 7A. Signal States During Power-down Mode

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