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SCC(4) Device Drivers Manual (alpha) SCC(4)

sccZilog serial communications interface

scc0 at ioasic?
scc1 at ioasic?

The scc driver provides support for the Zilog 8530 Serial Communications Controller (SCC) via the IOCTL asic on TURBOchannel-based alphas (the DEC 3000 series). Each scc device has two serial ports.

Input and output for each line may set to one of following baud rates; 50, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 9600, 19200, 38400, or 57600. Speeds up to 230400 are supported by the chip and the motherboard, but speeds higher than 57600 do not work reliably without an external clock signal.


The mapping from units to serial-hardware outlets is idiosyncratic.

intro(4), tty(4)

The scc driver first appeared in 4.4BSD.

The IOCTL asic provides internal DMA channels that can be programmed to transfer up to 4096 bytes of data into, or out, of an SCC without further software intervention. This feature of the ioctl asic is not yet supported.

The mapping from device-special files (major and minor number) to chip and port is arguably backwards.

May 31, 2007 OpenBSD-5.8