User`s guide

LZ87010 Advance User’s Guide External Memory
1/15/03 11-3
11.2 Signals
All of the external memory signals are shared with I/O ports, as shown in Table 11-1.
Port 2, Port 5, and Port 8 are used in their entirety for address and data buses, while two
bits of Port 1 provide output enable and write enable signals.
The 16-bit address uses two 8-bit ports. One of these, Port 2, is a high-current output port,
while the other, Port 8, is a general-purpose I/O port. Designers should note that the output
timing and characteristics of the two halves of the address are therefore not identical.
Table 11-1. External Memory Signals
SIGNAL
NAME
SIGNAL
TYPE
PIN
NUMBERS
PIN
TYPE
FUNCTIONAL
UNIT
SHARED
WITH
DESCRIPTION
nPSEN O 8 I/O
External
Memory
P1[7] External Memory Output Enable
nPSWR O 7 I/O
External
Memory
P1[6] External Memory Read/Write
XMA[15:8] O 25:18 O
External
Memory
P2
External Memory Address Bus,
Upper 8 Bits
XMA[7:0] O 35:28 I/O
External
Memory
P8
External Memory Address Bus,
Lower 8 Bits
XMD[7:0] I/O 17:10 I/O
External
Memory
P5 External Memory Data Bus