Z89139 Zilog., Z89139 Datasheet - Page 29

• Manufacturer Part Number: Z89139
• Description: Voice Processing Controllers
• Manufacturer: Zilog.

Zilog
Port 5 (P53-P50). Port 5 is a 4-bit, bidirectional, CMOS
compatible I/O port (Figure 16). These four I/O lines are
configured under software control independently as inputs
or outputs. Port 5 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.
DS97TAD0201
Open-Drain
OEN
Out
In
1.5
Z89138/139
2.3V Hysteresis
MCU
Figure 16. Port 5 Configuration
R = 500 K
P R E L I M I N A R Y
Port 5 is a bit programmable general-purpose I/O port. The
control registers for Port 5 are mapped into the expanded
register file (Bank F) of the Z8.
Auto Latch. The Auto Latch on Port 5 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.
Port 5
(I/O)
Voice Processing Controllers
Auto Latch
Pad
Z89138/Z89139
29
1