10
ispMACH 4A Family
Macrocell
The macrocell consists of a storage element, routing resources, a clock multiplexer, and initialization
control. The macrocell has two fundamental modes: synchronous and asynchronous (Figure
5). The mode
chosen only affects clocking and initialization in the macrocell.
In either mode, a combinatorial path can be used. For combinatorial logic, the synchronous mode will
generally be used, since it provides more product terms in the allocator.
SWAP
D/T/L
Q
AP
AR
Power-Up
Reset
PAL-Block
Initialization
Product Terms
From Logic Allocator
Block CLK0
Block CLK1
Block CLK2
Block CLK3
To Output and Input
Switch Matrices
Common PAL-block resource
Individual macrocell resources
From
PAL-Clock
Generator
D/T/L
Q
AP
AR
Power-Up
Reset
Individual
Initialization
Product Term
From Logic
Allocator
Block CLK0
Block CLK1
To Output and Input
Switch Matrices
Individual Clock
Product Term
From PAL-Block
Clock Generator
SWAP
17466G-010
Figure 5. Macrocell
17466G-009
a. Synchronous mode
b. Asynchronous mode