PSD4235G2V-10UI datasheet(45/100 Pages) STMICROELECTRONICS

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PSD4256G6V

This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.

Input Macrocells (IMC)

The CPLD has 24 Input Macrocells (IMC), one for

each pin on Ports A, B, and C. The architecture of

the Input Macrocells (IMC) is shown in Figure 16.

The Input Macrocells (IMC) are individually config-

urable, and can be used as a latch, register, or to

pass incoming Port signals prior to driving them

onto the PLD input bus. The outputs of the Input

Macrocells (IMC) can be read by the MCU through

the internal data bus.

The enable for the latch and clock for the register

are driven by a multiplexer whose inputs are a

product term from the CPLD AND Array or the

MCU Address Strobe (ALE/AS). Each product

term output is used to latch or clock four Input

Macrocells (IMC). Port inputs 3-0 can be con-

trolled by one product term and 7-4 by another.

Configurations for the Input Macrocells (IMC) are

specified by PSDsoft (see Application Note

AN1171). Outputs of the Input Macrocells (IMC)

can be read by the MCU via the IMC buffer. See

Figure 21, page 51 to Figure 26, page 57 for ex-

amples of the basic connections between the PSD

and some popular MCUs. The PSD Control input

pins are labeled as to the MCU function for which

they are configured. The MCU bus interface is

specified using the “I/O Ports”, on page 16.

Input Macrocells (IMC) can use Address Strobe

(ALE/AS, PD0) to latch address bits higher than

A15. Any latched addresses are routed to the

PLDs as inputs.

Input Macrocells (IMC) are particularly useful with

handshaking communication applications where

two processors pass data back and forth through

a common mailbox. Figure 18, page 46 shows a

typical configuration where the Master MCU writes

to the Port A Data Out Register. This, in turn, can

be read by the Slave MCU via the activation of the

“Slave-READ” output enable product term.

The Slave can also write to the Port A Input Mac-

rocells (IMC) and the Master can then read the In-

put Macrocells (IMC) directly.

Note that the “Slave-READ” and “Slave-Wr” sig-

nals are product terms that are derived from the

Slave MCU inputs READ Strobe (RD, CNTL1),

WRITE

Strobe

(WR/WRL,

CNTL0),

and

Slave_CS.

Figure 16. Input Macrocell

OUTPUT

MACROCELLS A

AND

MACROCELLS B

FEEDBACK

PORT

DRIVER

I/O PIN

INTERNAL DATA BUS

DIRECTION

MUX

ALE/AS

LATCH

INPUT MACROCELL

ENABLE (.OE)

D FF

INPUT MACROCELL _ RD

AI04926

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