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General Purpose Input/Output
LH75400/01/10/11 (Preliminary) User’s Guide
21-2
6/17/03
21.1 GPIO Features
The GPIO supports the following features.
• 10 GPIO ports
• Programmable port direction
• All ports but one default to inputs at System Reset
• Control word read-back capability.
All GPIO pins are multiplexed with other functions. Some GPIO pins have Schmitt Trigger
inputs. Some pins can have pull-ups and pull-downs that can be switched on or off under
software control.
21.2 GPIO Theory of Operation
There are 10 GPIO ports:
• Seven 8-bit ports
• Two 7-bit ports
• One 6-bit port.
GPIO ports are designated A through J. Pins of all ports, except Port J, can be configured
as either inputs or outputs. Port J is input only. Upon System Reset, all ports default to inputs.
Table 21-1. GPIO Ports
PORT PROGRAMMABLE PINS
A
8 Input/Output Pins
B
6 Input/Output Pins
C
8 Input/Output Pins
D
7 Input/Output Pins
E
8 Input/Output Pins
F
7 Input/Output Pins
G
8 Input/Output Pins
H
8 Input/Output Pins
I
8 Input/Output Pins
J
8 Input Pins