Zilog SCC

Developed from the earlier Zilog SIO devices (Z8443), the SCC added a number of serial-to-parallel modes that allowed internal implementation of a variety of data link layer protocols like Bisync, HDLC and SDLC.

One of the most famous users of the SCC was the Apple Macintosh SE computer line, which used the Z8530 to implement two serial ports on the back of the early designs, labeled "modem" and "printer".

[1] The SCC is essentially an updated version of the SIO, with more internal logic to allow it to directly implement a number of common data link layer protocols.

When used in traditional serial mode, the SCC could be set to use 5, 6, 7 or 8 bits/character, 1, 1+1⁄2, or 2 stop bits, odd, even or no parity, and automatically detected or generated break signals.

With network-like communications the SCC itself could cause the remote sender to stop transmission when the buffers were full, and thereby prevent data loss while the host was busy.

Plug compatible with the early versions, adding the 2x speed when used with the external clock, and a number of bug fixes and improvements in the link layer protocols.