Using Alternate I/O Functions; Uart 1 Modem Control - Wavecom GR64 Application Note

4

Using Alternate I/O functions

The following sections describe the alternate I/O functions provided by GR/GS64
Wireless CPUs.
4.1

UART 1 modem control

The UART 1 modem control alternate function provides full RS-232 modem control
signals. Some of the reasons to select UART 1 modem control alternate function are:
• Flow control is typically required to prevent serial buffer overruns when high-
speed UART data rates are used.
• Modem control enables the RTS/CTS hardware flow control mechanism. If standby
mode is required for low power consumption,
• DTR and DSR are used for sleep/wake handshaking. The Ring Indicator signal can
indicate receipt of incoming calls or messages.
• Plug-and-Play enumeration of serial devices requires modem control lines. If the
application is using the Windows driver to control GR/GS64 Wireless CPUs, the
UART 1 modem control alternate function must be enabled.
By factory default, the UART 1 modem control alternate function is selected. The
alternate function is disabled or enabled by using the *E2RS232 AT command.
AT*E2RS232=2 (disables UART 1 modem control)
OK
AT*E2RS232=0 (enables UART 1 modem control)
OK
The *E2RS232 settings are not retained across power downs. If the application wishes
to disable the UART 1 modem control alternate function, it must do so after each
Wireless CPU restart. The application may then use the modem control pins for GPIO
purposes.
APPLICATION NOTE
GR/GS64 General Purpose and
Alternate Function I/O
Page: 8/13
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