R
XC4000E and XC4000X Series Field Programmable Gate Arrays
Passive
Slew Rate
Control
Pull-Up/
Pull-Down
T
Flip-Flop
D
Q
Out
Output
Buffer
CE
Pad
Output
Clock
I
1
Input
Buffer
Flip-
Flop/
Latch
I
2
Q
D
Delay
Clock
Enable
CE
Input
Clock
6
X6704
Figure 15: Simplified Block Diagram of XC4000E IOB
Passive
Pull-Up/
Pull-Down
Slew Rate
Control
T
Output MUX
0
1
Flip-Flop
Out
D
Q
Output
Buffer
CE
Pad
Input
Buffer
Output Clock
I
I
1
2
Flip-Flop/
Latch
Delay
Q
Delay
Q
D
D
Latch
G
Clock Enable
Input Clock
CE
Fast
Capture
Latch
X5984
Figure 16: Simplified Block Diagram of XC4000X IOB (shaded areas indicate differences from XC4000E)
May 14, 1999 (Version 1.6)
6-21
ETC [ ETC ]
