Z86C61 Datasheet, PDF (14/46 Pages) Zilog, Inc. – CMOS Z8 MICROCONTROLLER

PIN FUNCTIONS (Continued)
Z86C61/62/96
Z8^® MICROCONTROLLER
Port 1 (P17-P10). Port 1 is an 8-bit, byte programmable,
bidirectional, TTL compatible port. It has multiplexed Ad-
dress (A7-A0) and Data (D7-D0) ports. For Z86C61/62/96,
these eight I/O lines can be programmed as Input or
Output lines or can be configured under software control
as an address/data port for interfacing external memory.
When used as an I/O port, Port 1 may be placed under
handshake control. In this configuration, Port 3 line P33
and P34 are used as the handshake controls RDY1 and
/DAV1.
Memory locations greater than 16,384 are referenced
through Port 1. To interface external memory, Port 1 must
be programmed for the multiplexed Address/Data mode.
If more than 256 external locations are required, Port 0
must output the additional lines.
Port 1 can be placed in high-impedance state along with
Port 0, /AS, /DS, and R//W, allowing the microcontroller to
share common resources in multiprocessor and DMA
applications. Data transfers can be controlled by assign-
ing P33 as a Bus Acknowledge input, and P34 as a Bus
request output (Figure 11).
MCU
8
Port 1
(AD7-AD0)
Handshake Controls
/DAV1 and RDY1
(P33 and P34)
OEN
PAD
Out
TTL Level Shifter
In
R ≈ 500 KΩ
Figure 11. Port 1 Configuration
Auto Latch
14