The SCC, short for Serial Communication Controller, is a family of serial port driver integrated circuits made by Zilog. The primary members of the family are the Z8030/Z8530, and the Z85233. 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. The SCC could be set up as a conventional RS-232 port for driving legacy systems, or alternately as a RS-422 port for much higher performance, up to 10 Mbit/s. Implementation details generally limited performance to 5 Mbit/s or less. One of the most famous users of the SCC was the Apple Macintosh computer line, which used the Z8530 to implement two serial ports on the back of the early designs, labeled "modem" and "printer". Description Traditional serial communications are normally implemented using a device known as a UART, which translates data from the computer bus's internal parallel format to serial and back. This allows the computer to send data serially simply by placing data in memory in its own internal format, say 16-bit little-endian, and the UART will convert this to serial form and send it. Generally there were different UARTs for each computer architecture, with the goal of being as low-cost as possible. A good example is the Zilog Z-80 SIO from 1977, designed to work with the widely used Zilog Z80 to provide two serial ports with relatively high speeds up to 800 kbit/s. 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. To start with, the SCC included a hardware implementation of the cyclic redundancy check (CRC), which allowed it to check, flag and reject improper data without the support of the host computer. Higher-level protocols included BiSync, HDLC and SDLC. HDLC is better known in its implementation in the modem-oriented LAPM protocol, part of V.42. By moving the implementation of these protocols to hardware, the SCC made it easy to implement local area networking systems, like IBM's SNA, without the need for the host CPU to handle these details. When used in traditional serial mode, the SCC could be set to use 5, 6, 7 or 8 bits/character, 1, , or 2 stop bits, odd, even or no parity, and automatically detected or