Inside Macintosh: Open Transport /

Chapter 16 - Serial Endpoint Providers / Serial Endpoint Providers Reference

Serial-Specific Commands

I_SetSerialXOn

This command causes the serial port to send an XON character. A value of kOTSerialSendXOnIfXOffTrue causes it to be sent only if the endpoint is in the XOFF state (that is, if the last input flow-control character sent was XOFF), while a value of kOTSerialSendXOnAlways unconditionally sends the character. The following line of code unconditionally sends an XON character:

OTIoctl(theSerialEndpoint, I_SetSerialXOn, kOTSerialSendXOnAlways);

Sending the XON character unconditionally is equivalent to using a serial driver control call with a csCode value of 24, and sending the XON character when an endpoint is in an XOFF state is equivalent to using a csCode value
of 23.