Rainbow Electronics ATF2500CQL - Manual (Page 5)

5
ATF2500C Family
0777G–12/01
Input Diagram
I/O Diagram
Functional
Logic Diagram
Description
The ATF2500C functional logic diagram describes the interconnections between the input,
feedback pins and logic cells. All interconnections are routed through the single global bus.
The ATF2500Cs are straightforward and uniform PLDs. The 24 macrocells are numbered 0
through 23. Each macrocell contains 17 AND gates. All AND gates have 172 inputs. The five
lower product terms provide AR1, CK1, CK2, AR2, and OE. These are: one asynchronous
reset and clock per flip-flop, and an output enable. The top 12 product terms are grouped into
three sum terms, which are used as shown in the macrocell diagrams.
Eight synchronous preset terms are distributed in a 2/4 pattern. The first four macrocells share
Preset 0, the next two share Preset 1, and so on, ending with the last two macrocells sharing
Preset 7.
The 14 dedicated inputs and their complements use the numbered positions in the global bus
as shown. Each macrocell provides six inputs to the global bus: (left to right) feedback F2
(1)
true and false, flip-flop Q1 true and false, and the pin true and false. The positions occupied by
these signals in the global bus are the six numbers in the bus diagram next to each macrocell.
Note: 1. Either the flip-flop input (D/T2) or output (Q2) may be fed back in the ATF2500Cs.
INPUT