PSD4235G2 datasheet(34/89 Pages) STMICROELECTRONICS

34 / 89 page

PSD4235G2

34/89

COMPLEX PLD (CPLD)

The CPLD can be used to implement system logic

functions, such as loadable counters and shift reg-

isters, system mailboxes, handshaking protocols,

state machines, and random logic. The CPLD can

also be used to generate eight External Chip Se-

lect (ECS0-ECS7), routed to Port C or Port F.

Although External Chip Select (ECS0-ECS7) can

be produced by any Output Macrocell (OMC),

these eight External Chip Select (ECS0-ECS7) on

Port C or Port F do not consume any Output Mac-

rocells (OMC).

As shown in Figure 12, the CPLD has the following

blocks:

24 Input Macrocells (IMC)

16 Output Macrocells (OMC)

Product Term Allocator

AND Array capable of generating up to 196

product terms

Four I/O Ports.

Each of the blocks are described in the sections

that follow.

The Input Macrocells (IMC) and Output Macrocells

(OMC) are connected to the PSD internal data bus

and can be directly accessed by the MCU. This

enables the MCU software to load data into the

Output Macrocells (OMC) or read data from both

the Input and Output Macrocells (IMC and OMC).

This feature allows efficient implementation of sys-

tem logic and eliminates the need to connect the

data bus to the AND Array as required in most

standard PLD macrocell architectures.

Figure 14. Macrocell and I/O Port

I/O PORTS

CPLD MACROCELLS

INPUT MACROCELLS

LATCHED

ADDRESS OUT

MUX

PDR

DATA

PRODUCT TERM

ALLOCATOR

DIR

REG.

SELECT

INPUT

PRODUCT TERMS

FROM OTHER

MACROCELLS

POLARITY

SELECT

UP TO 10

PRODUCT TERMS

CLOCK

SELECT

DI LD

D/T

D/T/JK FF

SELECT

PT CLEAR

CLOCK

GLOBAL

CLOCK

PT OUTPUT ENABLE (OE)

MACROCELL FEEDBACK

I/O PORT INPUT

ALE/AS

PT INPUT LATCH GATE/CLOCK

MCU LOAD

PT PRESET

MCU DATA IN

COMB.

/REG

SELECT

MCU ADDRESS / DATA BUS

MACROCELL

OUT TO

MCU

DATA

LOAD

CONTROL

CPLD OUTPUT

I/O PIN

AI04945

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