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Chapter 8
General Purpose
Input/Output
The LH79524 and LH79525 have a robust set of General Purpose Input/Output (GPIO)
pins that can be used for any required input or output function. The LH79524 has 14 ports,
providing 108 pins of GPIO. The LH79525 has 11 ports, with 86 individual pins. All descrip-
tions, unless noted, apply to both the LH79524 and LH79525.
8.1 Theory of Operation
The GPIO pins are multiplexed with other functions. Some of the GPIO ports have
Schmitt triggers, and some have pull-up or pull-down resistors built in (See Table 8-2).
Table 8-1 summarizes the configuration of each port. Note that Port J is input only, and
Port M is output only. At reset, all ports except Ports J and M are configured for input. Ports
J and M are not configured as GPIO at reset.
8.1.1 Port Configuration
Port pins can be configured individually as inputs or outputs (except, of course, Ports J and
M). The direction of each pin is programmed using the Data Direction Registers (P1DDRx
and P2DDRx). Data for output pins is written to the port Data Register (P1DRx and
P2DRx). Input data is read from the same registers.
Table 8-1. GPIO Ports
PORT
LH79524 GPIO
A
8 Input/Output Pins
B
8 Input/Output Pins
C
8 Input/Output Pins
D
8 Input/Output Pins
E
8 Input/Output Pins
F
8 Input/Output Pins
G
8 Input/Output Pins
H
8 Input/Output Pins
I
8 Input/Output Pins
J
8 Input Pins
K
8 Input/Output Pins
L
8 Input/Output Pins
M
8 Output Pins
N
4 Input/Output Pins
Version 1.0
LH79525 GPIO
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input/Output Pins
8 Input Pins
Not Available
Not Available
6 Output Pins
Not Available
8-1
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