Z89175 Datasheet, PDF (28/68 Pages) Zilog, Inc. – Voice Processing Controllers

Z89175/Z89176
Voice Processing Controllers
PIN FUNCTIONS (Continued)
Port 4 (P47-P40). Port 4 is an 8-bit, bidirectional, CMOS
compatible I/O port (Figure 15). These eight I/O lines are
configured under software control independently as inputs
or outputs. Port 4 is always available for I/O operation. The
input buffers are Schmitt-triggered. Bits programmed as
outputs can be globally programmed as either push-pull or
open-drain.
Zilog
Port 4 is a bit programmable general-purpose I/O port. The
control registers for Port 4 are mapped into the expanded
register file (Bank F) of the Z8.
Auto Latch. The Auto Latch on Port 4 puts valid CMOS
levels on all CMOS inputs which are not externally driven.
Whether this level is 0 or 1 cannot be determined. A valid
CMOS level, rather than a floating node, reduces exces-
sive supply current flow in the input buffer.
Open-Drain
OEN
Z89175/176
MCU
Port 4
(I/O)
Out
In
28
1.5
2.3V Hysteresis
R = 500 KΩ
Figure 15. Port 4 Configuration
PRELIMINARY
Pad
Auto Latch
DS97TAD0100