PSD813F2 datasheet(55/110 Pages) STMICROELECTRONICS

55 / 110 page

55/110

PSD813F2, PSD833F2, PSD834F2, PSD853F2, PSD854F2

Address In Mode

For MCUs that have more than 16 address sig-

nals, the higher addresses can be connected to

Port A, B, C, and D. The address input can be

latched in the Input Macrocell (IMC) by Address

Strobe (ALE/AS, PD0). Any input that is included

in the DPLD equations for the SRAM, or primary or

secondary Flash memory is considered to be an

address input.

Data Port Mode

Port A can be used as a data bus port for a MCU

with a non-multiplexed address/data bus. The

Data Port is connected to the data bus of the MCU.

The general I/O functions are disabled in Port A if

the port is configured as a Data Port.

Peripheral I/O Mode

Peripheral I/O mode can be used to interface with

external peripherals. In this mode, all of Port A

serves as a tri-state, bi-directional data buffer for

the MCU. Peripheral I/O Mode is enabled by set-

ting Bit 7 of the VM Register to a ’1.’ Figure 27

shows how Port A acts as a bi-directional buffer for

the MCU data bus if Peripheral I/O Mode is en-

abled. An equation for PSEL0 and/or PSEL1 must

be written in PSDabel. The buffer is tri-stated

when PSEL0 or PSEL1 is not active.

Figure 27. Peripheral I/O Mode

PSEL0

PSEL1

PSEL

VM REGISTER BIT 7

PA0 - PA7

D0 - D7

DATA BUS

AI02886

PSD813F2 データシート(PDF) 55 Page - STMicroelectronics

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