Inside Macintosh: Open Transport /

Chapter 16 - Serial Endpoint Providers / Serial Endpoint Providers Reference

Serial-Specific Commands

I_SetSerialXOff

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

OTIoctl(theSerialEndpoint, I_SetSerialXOff, kOTSerialSendXOffAlways);

Sending the XOFF character unconditionally is equivalent to using a serial driver control call with a csCode value of 26, and sending the XOFF character when an endpoint is in an XON state is equivalent to using a csCode value
of 25.