About the Serial Drivers
About the Serial Drivers ยทSerial communications and the Macintosh
In the Macintosh, RAM and ROM serial device drivers handle full-duplex
asynchronous data transmission between applications and serial devices. In
Mac versions using the 128K and larger ROMs, one serial device driver
supersedes the older RAM and ROM versions. The newer ROM-based serial
driver is backward compatible with programs written for earlier systems as
long as your program includes the older RAM drivers as 'SERD'-type
resources in their resource fork and continues to use the RAMSDOpen and Although the newer ROM-based driver is backward compatible, Apple no
OpenDriver. Although details of the drivers are given here, use of OpenDriver will ensure that your code is user-friendly and compatible with future versions of the System Software.
Full-duplex refers to the ability to send and receive at the same time.
Asynchronous means that the Mac and its communications partner have their
own timers, don't share timing information, and don't depend on fixed timing