Z8
®
CPU
User Manual
UM001604-0108
Input/Output Ports
45
General I/O Mode
Port 0 can be an 8-bit, bidirectional, CMOS or TTL compatible I/O port. These eight I/O
lines can be configured under software control as a nibble I/O port (P03–P00 input/output
and P07–P04 input/output), or as an address port for interfacing external memory. The
input buffers can be Schmitt-Triggered, level shifted, or a single-trip point buffer and can
be nibble programmed. Either nibble output can be globally programmed as push–pull or
open-drain. Low EMI output buffers in some cases can be globally programmed by the
software as an OTP program option or as a ROM mask option. In such cases, the Z8
®
MCU features autolatches that are hardwired to the inputs. Refer to the specific Z8 MCU
product specification for the exact input/output buffer features that are available (see
on page 46 and
Figure 29. Ports 0, 1, 2 Generic Block Diagram
Handshake
Logic
Internal
Timing
Handshake
Selected
RDY/DAV
DAV/RDY
Port I/O
Lines
Input
Buffer
Input
Register
Handshake
Logic
Output
Buffer
Output
Register
Output
Enable
Internal
Bus
Write
Port
Read
Port
E
8
8
8
8
8
8
8
