Epson PX-8 - Page 274

REV.-A
70008 Main CPU
1 . Location: MAPLE board, 4A
2. Pin Assignments
All
Alz
AI3
AI4
Als
rZJ
D4
03
Os
D6
+5V
Oz
07
Do
01
INT
NMI
HALT
MREQ
IORQ
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
-"
AID
A9
As
A7
A6
As
A4
A3
Az
A I
AD
ONO
RFSH
M I
RESET
8USRQ
WAIT
8USAK
WR
RO
Table 7-1 70008 MAIN CPU Pin Assignments
Pin No.
Signal Name
In/Out Function
-5
ABO-15
Tri-state output A 1 6-bit address bus which outputs a
30-40 (Address Bus)
active high
memory address or I/O device number. It
outputs the lower 7 bit D-RAM address for
memory refresh.
7-10 DBO-15
Tri-state input
An 8-bit data bus which is used for data
12-15
(Data Bus) and output
transfer between memory or an I/O device
active high
and main CPU.
-
27
Ml Output
A signal which indicates that the starting
(Machine
active
low machine cycle is the OP code fetch cycle.
Cycle one)
--
19
MRQ
Tri-state output: A signal which indicates that the address
(Memory Request)
active
low
information required for the memory read/
write is output on the address bus. It is also
output during memory refresh for synchroni-
zation.
7-3