ZiLOG Z8 Technical Manual

6.1 INTRODUCTION
The ROM versions of the ZS microcomputer have 40
external pins, of which 32 are programmable I/O
pins. The remaining S pins are used for power and
control. Up to 16 I/O pins can be configured as
an external memory interface. This interface
function is the subject of this chapter. The I/O
mode of these pins is described in Chapter 9.
6.2 PIN DESCRIPTIONS
AS. Address Strobe (output, active low, 3-state,
pin 9). Address Strobe is pulsed Low once at the
beginning of each machine cycle. The rising edge
of AS indicates that addresses, Read/Write (R/W),
and Data Memory (OM) signals, are valid when out-
put for external program or data memory trans-
fers. Under program control, AS can be placed in
RESET
+5V
R/W GND
OS
XTAL1
AS
XTAL2
PO
o
P20
POI
P2
1
P0
2
P2
2
PORTO
P2
3
PORT 2
(NIBBLE
P0
3
(BIT PRO·
Chapter 6
External Interface
(Z8601, Z8611)
a high-impedance state along with Ports 0 and 1,
Data Strobe (55), and R/W.
DS. Data Strobe (output, active low, 3-state,
pin 8). Data Strobe provides the timing for data
movement to or from Port 1 for each external
memory transfer. During a Write cycle, data out
is valid at the leading edge of OS. During a Read
cycle, data in must be valid prior to the trailing
edge of OS. 55 can be placed in a high-impedance
state along with Ports 0 and 1, AS, and R/W.
R/W.
Read/Write. (output, 3-state, pin 7).
Read/Write determines the direction of data trans-
fer for external memory transactions. R/W is Low
when writing to external program or data memory,
and High for all other transactions. R/W can be
placed in a high-impedance state along with Ports
o and 1, AS, and OS.
+5V 40
P3
6
XTAL2 2
39 P3
1
XTAL1 3 38
P2
7
P3
7
4
37 P2
6
P3
0
5 36 P2
s
RESET
6
35
P2
4
R/W
7 34
P2
3
OS
8 33 P2
2
PROGRAMMABLE)
P0
4
P2
4
GRAMMABLE)
AS
9 32
P2
1
P3
s
10
28601/11
31
P2
0
GND
11
MCU
30
P3
3
P3
2
12 29
P3
4
PO
o
13 28 P1
7
POI
14 27
P1
6
P0
2
15 26
P1
s
P0
3
16 25
P1
4
P0
4
17 24
P1
3
PO
s
18 23
P1
2
POe
19
22
P1
1
P0
7
20
21
P1
0
1/0 OR Ae-A'5
1/0
PO
s
28601111 P2
s
POe
MCU
P2
e
P0
7
P2
7
P1
0
P3
0
P1
1
P3
1
P1
2
P3
2
PORT 3
PORT 1
P1
3
P3
3
(FOUR INPUT;
(BYTE
FOUR OUTPUT)
PROGRAMMABLE)
P1
4
P3
4
SERIAL AND
1/0 OR ADo-AD7
PARALLEL 1/0
P1
s
P3
s
AND
CONTROL
P1
e
P3
e
P1
7
P3
7
Figure 6-1. Z8601/11 Pin Functions Figure 6-2. Z8601/11 Pin Assignments
3047 -031, 2037-002
6-1

ZiLOG Z8 Specifications

General

Brand	ZiLOG
Model	Z8
Category	Desktop
Language	English