User's Manual

GM862-QUAD / PY Hardware User Guide

1vv0300748 Rev. 1 - 24/10/06

8 General Purpose I/O

The general purpose I/O pins can be configured to act in three different ways:

- input

- output

- alternate function (internally controlled)

Input pins can only be read and report the digital value (high or low) present on the pin at the read

time; output pins can only be written or queried and set the value of the pin output; an alternate

function pin is internally controlled by the GM862-QUAD / PY firmware and acts depending on the

function implemented.

Not all GPIO pins support all these three modes:

- GPIO1 is an INPUT ONLY

- GPIO2 is an OUTPUT ONLY (open collector)

- GPIO3, GPIO4, GPIO8 to GPIO13 support both input or output mode but not Alternate function.

- GPIO5 supports all three modes and can be input, output, RFTXMON output (Alternate function)

- GPIO6 supports all three modes and can be input, output, ALARM output (Alternate function)

- GPIO7 supports all three modes and can be input, output, BUZZER output (Alternate function)

All GPIO pins except from GPIO1 and GPIO2 that are buffered with a transistor, are 2.8V CMOS

signals and their interface levels are the same specified in the paragraph 5 Serial Port.

8.1 Logic level specifications

Where not specifically stated, all the interface circuits work at 2.8V CMOS logic levels.

The following table shows the logic level specifications used in the GM862 interface circuits:

Absolute Maximum Ratings -Not Functional

Parameter Min Max

Input level on any

digital pin when on

-0.3V +3.75V

Input voltage on

analog pins when on

-0.3V +3.0 V