Philips Semiconductors

Product specification

PZ3064

64 macrocell CPLD

1997 Mar 05

85

Macrocell Architecture

Figure 3 shows the architecture of the macrocell used in the

CoolRunner

™ family. The macrocell consists of a flip-flop that can be

configured as either a D or T type. A D-type flip-flop is generally

more useful for implementing state machines and data buffering. A

T-type flip-flop is generally more useful in implementing counters. All

CoolRunner

™ family members provide both synchronous and

asynchronous clocking and provide the ability to clock off either the

falling or rising edges of these clocks. These devices are designed

such that the skew between the rising and falling edges of a clock

are minimized for clocking integrity. There are 4 clocks available on

the PZ3064 device. Clock 0 (CLK0) is designated as the

“synchronous” clock and must be driven by an external source.

Clock 1 (CLK1), Clock 2 (CLK2), and Clock 3 (CLK3) can either be

used as a synchronous clock (driven by an external source) or as an

asynchronous clock (driven by a macrocell equation).

Two of the control terms (CT0 and CT1) are used to control the

Preset/Reset of the macrocell’s flip-flop. The Preset/Reset feature

for each macrocell can also be disabled. Note that the Power-on

Reset leaves all macrocells in the “zero” state when power is

properly applied. The other 4 control terms (CT2–CT5) can be used

to control the Output Enable of the macrocell’s output buffers. The

reason there are as many control terms dedicated for the Output

Enable of the macrocell is to insure that all CoolRunner

™ devices

are PCI compliant. The macrocell’s output buffers can also be

always enabled or disabled. All CoolRunner

™ devices also provide a

Global Tri-State (GTS) pin, which, when pulled Low, will 3-State all

the outputs of the device. This pin is provided to support “In-Circuit

Testing” or “Bed-of-Nails Testing”.

There are two feedback paths to the ZIA: one from the macrocell,

and one from the I/O pin. The ZIA feedback path before the output

buffer is the macrocell feedback path, while the ZIA feedback path

after the output buffer is the I/O pin ZIA path. When the macrocell is

used as an output, the output buffer is enabled, and the macrocell

feedback path can be used to feedback the logic implemented in the

macrocell. When the I/O pin is used as an input, the output buffer

will be 3-Stated and the input signal will be fed into the ZIA via the

I/O feedback path, and the logic implemented in the buried

macrocell can be fed back to the ZIA via the macrocell feedback

path. It should be noted that unused inputs or I/Os should be

properly terminated.

CT2

CT3

CT4

CT5

GND

INIT

(P or R)

D/T

Q

CLK0

CLK0

CLK1

CLK1

TO ZIA

GND

CT0

CT1

GND

GTS

CLK2

CLK2

CLK3

CLK3

SP00457

Figure 3.

PZ3064 Macrocell Architecture