Z86D99 ZILOG [Zilog, Inc.], Z86D99 Datasheet - Page 33

• Manufacturer Part Number: Z86D99
• Description: Low-Voltage Micro controllers with ADC
• Manufacturer: ZILOG [Zilog, Inc.]

PS003807-1002
Out
In
Open-Drain
I/O
Figure 12. General Input/Output Pin
Read/Write Operations
The ports are accessed as general-purpose registers. Port registers are written by
specifying the port register as an instruction’s destination register. Writing to a port
causes data to be stored in the output register of the port, and reflected externally
on any bit configured as an output.
Ports are read by specifying the port register as the source register of an instruc-
tion. When an output bit is read, data on the external pin is returned. Under normal
loading conditions, returning data on the external pin is equivalent to reading the
output register. However, if a bit is defined as an open-drain output, the data
returned is the value forced on the output pin by the external system. This value
might not be the same as the data in the output register. Reading input bits also
returns data on the external pins.
P
R
E
L
I
M
Z86D990/Z86D991 OTP and Z86L99X ROM
I
Low-Voltage Microcontrollers with ADC
N
A
OTP/Mask
R
Option
Pull-Up
Y
Pad
Note: * Pull-up resistance is
about 200 K
75 K
tolerance.
V
CC
*
at 5.0 V with +50%
at 2.3 V and
26