PSD211R datasheet(12/51 Pages) STMICROELECTRONICS

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Port

Configurations

I/O or low-order (latched) address lines

I/O and/or CS0–CS7

A16-A18 or CS8-CS10

PSD211R Family

The PSD211R operates in 8-bit address/data mode, enabling it to interface directly to a

variety of 8-bit multiplexed microcontrollers. It works as follows: the address/data bus

(AD0-AD7) is bi-directional and permits the latching of the address when the ALE/AS signal

is active. On the same pins, the data is read from or written to the device, depending on the

state of the control signals (WR, RD, etc.). You should connect your MCU according to the

following figure. Ports A through C can be configured according to Table 3, below.

Your

8-bit

MCU

PSD211R

AD0 -AD7

I /O or A0 - A7

A8 -A15

ALE/AS

PSEN

R/ W or WR

RD/E

A19 / CSI

RESET

A16-A181

I /O or CS0 - CS7

CS8 - CS10

Figure 3. Connecting a PSD211R to an 8-Bit Multiplexed-Bus MCU

8.0

Operating Mode

Table 3. Bus and Port Configuration Options

9.0

Programmable

Address

Decoder (PAD)

NOTE: 1. Connect A16-A18 to Port C if your MCU outputs more than 16 bits of address.

The PSD211R contains two programmable arrays, referred to as PAD A and PAD B

(Figure 4). PAD A is used to generate chip select signals derived from the input address to

the internal EPROM blocks and I/O ports.

PAD B outputs to Ports B and C for off-chip usage. PAD B can also be used to extend the

decoding to select external devices or as a random logic replacement.

PAD A and PAD B receive the same inputs. The PAD logic is configured by PSDsoft based

on the designer’s input. The PAD’s non-volatile configuration is stored in a re-programmable

CMOS EPROM. Windowed packages are available for erasure by the user. See Table 4 for

a list of PAD A and PAD B functions.

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