UPSD3233 datasheet(117/170 Pages) STMICROELECTRONICS

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uPSD3234A, uPSD3234BV, uPSD3233B, uPSD3233BV

Product Term Allocator

The CPLD has a Product Term Allocator. PSDsoft

uses the Product Term Allocator to borrow and

place product terms from one macrocell to anoth-

er. The following list summarizes how product

terms are allocated:

–

McellAB0-McellAB7 all have three native

product terms and may borrow up to six more

–

McellBC0-McellBC3 all have four native

product terms and may borrow up to five more

–

McellBC4-McellBC7 all have four native

product terms and may borrow up to six more.

Each macrocell may only borrow product terms

from certain other macrocells. Product terms al-

ready in use by one macrocell are not available for

another macrocell.

If an equation requires more product terms than

are available to it, then “external” product terms

are required, which consume other Output Macro-

cells (OMC). If external product terms are used,

extra delay is added for the equation that required

the extra product terms.

This is called product term expansion. PSDsoft

Express performs this expansion as needed.

Loading and Reading the Output Macrocells

(OMC). The Output Macrocells (OMC) block oc-

cupies a memory location in the MCU address

space, as defined by the CSIOP block (see the

section

entitled

I/O

PORTS

(PSD

MODULE), page 119). The flip-flops in each of the

16 Output Macrocells (OMC) can be loaded from

the data bus by a MCU. Loading the Output Mac-

rocells (OMC) with data from the MCU takes prior-

ity over internal functions. As such, the preset,

clear, and clock inputs to the flip-flop can be over-

ridden by the MCU. The ability to load the flip-flops

and read them back is useful in such applications

as loadable counters and shift registers, mailbox-

es, and handshaking protocols.

Data can be loaded to the Output Macrocells

(OMC) on the trailing edge of WRITE Strobe (WR,

edge loading) or during the time that WRITE

Strobe (WR) is active (level loading). The method

of loading is specified in PSDsoft Express Config-

uration.

Figure 61. CPLD Output Macrocell

ALLOCATOR

MASK

REG.

PT CLK

CLKIN

FEEDBACK (.FB)

PORT INPUT

MUX

POLARITY

SELECT

CLR

DIN

COMB/REG

SELECT

PORT

DRIVER

INPUT

MACROCELL

I/O PIN

MACROCELL

ALLOCATOR

MCU DATA BUS

D [ 7:0]

DIRECTION

CLEAR (.RE)

PROGRAMMABLE

FF (D / T/JK /SR)

ENABLE (.OE)

PRESET(.PR)

MACROCELL CS

AI06617

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