Legacy Document

Inside Macintosh: Devices /

Chapter 6 - Power Manager / Power Manager Reference

Power Manager Routines / Controlling Serial Power

BOff

You can use the BOff procedure to turn off the power to serial port B and to the internal modem.

PROCEDURE BOff;

DESCRIPTION

The BOff procedure switches off power to the SCC and the -5 volt supply if serial port A is not in use. If the internal modem is installed, connected to port B, and switched on, this procedure switches off power to the modem. Otherwise, the BOff procedure switches off power to the serial driver chips, unless they are being used by port A.

ASSEMBLY-LANGUAGE INFORMATION

The MPW development system provides an assembly-language macro to execute the BOff routine. That macro calls the _SerialPower trap. To call the _SerialPower trap directly, you must first put a longword routine selector in the D0 register. For BOff, the routine selector is $80.