External Memory Interface Diagram Examples B-3

Figure B.3 128 Kbytes, 256 Kbytes, 512 Kbytes, or 1 Mbyte Interface with 150 nsMemory
LSI53C875A
27C020-15/
MOE/
OE
MCE/ CE
8
MAD[7:0]
Bus
8
A[7:0]
6
A[15:8]
VDD
MAS0/
MAS1/
Note:MAD[ 2:0]pulled L OWinter nally.MAD bus sense logic enabled for 128, 256, 512 Kbytes, or 1 Mbyte of fast
memory (150 ns devices @ 33 MHz). The HCT374s may be replaced with HCT377s.
GPIO4
MWE/
VPP
Control
+12V VPP
WE
Optional- for Flash Memory only, not
requiredfor EEPROMS.
28F020-15/
Socket
D[7:0]
MAD3 4.7K
D0
CK
Q0
Q3
4HCT377
MAD[3:0]
Bus
E
A[19:16]
D0
CK
Q0
QE
HCT374
D7 Q7
D0
CK
Q0
QE
HCT374
D7 Q7
D3