PSD413A2 datasheet(41/123 Pages) STMICROELECTRONICS

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PSD4XX Family

Pin Name

Function

LDS

R/W

WRL

PE0

BHE

PSEN

WRH

UDS

SIZ0

PE1

ALE

AD0

BLE

Table 6. Alternate Pin Functions

9.2.2 PSD4XX Interface To a Multiplexed Bus

Figure 20 shows a typical connection to a microcontroller with a multiplexed bus. The

ADIO port of the PSD4XX is connected directly to the microcontroller address/data bus

(AD0-AD15 for 16 bit bus). The ALE input signal latches the address lines internally. In a

read bus cycle, data is driven out through the ADIO Port transceivers after the specified

access time. The internal ADIO Port connection for a 16 bit multiplexed bus is shown in

Figure 21. The ADIO Port is in tri-state mode if none of the PSD4XX internal devices are

selected.

9.2.3 PSD4XX Interface To Non-Multiplexed Bus

Figure 22 shows a PSD4XX interfacing to a microcontroller with a non-multiplexed

address/data bus. The address bus is connected to the ADIO Port, and the data bus is

connected to Port C and/or Port D, depending on the bus width. There is no need for the

ADIO Port to latch the address internally, but the user is offered the option to do so in the

PSD4XX PSDsoft Software. The data Ports are in tri-state mode when the PSD4XX is not

accessed by the microcontroller.

The PSD4XX

Architecture

(cont.)

PSD413A2 Datasheet(PDF) 41 Page - STMicroelectronics