SHIP:Port:uart:txControl

Portvar	Data Type	Permissions	Description
txControl†	UART_FLAG	Read/Write	Sets how the hardware tx control line functions for full/half duplex transceiver control (default UART_FLAGS.TXC_UNUSED).

^†see GRM

The UARTS on most new platforms, for example, the SIM231 have a transmit control hardware signal present on the various communications connectors. This transmit control signal can be set to go active when the UART is transmitting a message (i.e. packet), enabling half duplex control of an external transceiver.

There are four options for this control line, set by the state of the txControl portvar with one of the UART_FLAG constants:

• UART_FLAGS.TXC_UNUSED -- do not drive the txControl line
• UART_FLAGS.TXC_DRIVE_HI -- push-pull drive the txControl line, active high
• UART_FLAGS.TXC_DRIVE_LO -- push-pull drive the txControl line, active low
• UART_FLAGS.TXC_OPEN_DRAIN -- open-drain drive the txControl line, active low

The line is "active" during packet transmission.

For example, on the SIM231 the hardware signal P42/AN002/IRQ10-XU_TE is present on the JST16 connector J4 pin 13 as well as the 60 pin docking connector J2 pin 39. This pin can be used to control an external transciever (for example, an RS422, 232, or 485 transceiver). If the external transceiver has an active high transmit-enable input, you can enable this hardware signal to go active high whenever a packet is being transmitted from UART0 by including this statement in a suitable script:

platform.UART0.txControl = platform.UART_FLAGS.TXC_DRIVE_HI;