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TC65 Hardware Interface Description

Confidential / Released

TC65_HD_V02.000 Page 72 of 120 08.06.2006

3.17 GPIO Interface

The TC65 has 10 GPIOs for external hardware devices. Each GPIO can be configured for

use as input or output. All settings are AT command controlled.

The GIPO related AT commands are the following: AT^SPIO, AT^SCPIN, AT^SCPOL,

AT^SCPORT, AT^SDPORT, AT^SGIO, AT^SSIO. A detailed description can be found in

[1].

When the TC65 starts up, all GPIO pins are set to high-impedance state after initializing, as

described in Chapter

3.3.2. Therefore, it is recommended to connect pull-up or pull-down

resistors to all GPIO pins you want to use as output. This is necessary to keep these pins

from floating or driving any external devices before all settings are done by AT command (at

least AT^SPIO, AT^SCPIN), and after closing the GPIOs again.

3.17.1 Using the GPIO10 Pin as Pulse Counter

The GPIO10 pin can be assigned two different functions selectable by AT command:

• The AT^SCPIN command configures the pin for use as GPIO.

• With AT^SCCNT and AT^SSCNT the pin can be configured and operated as pulse

counter.

Both functions exclude each other. The pulse counter disables the GPIO functionality, and

vice versa, the GPIO functionality disables the pulse counter. Detailed AT command

descriptions can be found in

[1].

The pulse counter is designed to measure signals from 0 to 1000 pulses per second. It can

be operated either in Limit counter mode or Start-Stop mode. Depending on the selected

mode the counted value is either the number of pulses or the time (in milliseconds) taken to

generate a number of pulses specified with AT^SCCNT.

In Limit counter mode, the displayed measurement result (URC “^SSCNT: <count>”) implies

an inaccuracy <5ms. In Start-Stop mode, you can achieve 100% accuracy if you take care

that no pulses are transmitted before starting the pulse counter (AT^SSCNT=0 or 1) and

after closing the pulse counter (AT^SSCNT=3).

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