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Annotation of lucent/sys/man/3/async, revision 1.1.1.1

1.1       root        1: .TH ASYNC 3 
                      2: .SH NAME
                      3: async \- framing for a serial line to Datakit
                      4: .SH SYNOPSIS
                      5: .nf
                      6: .B
                      7: ctlfd = open(".../ctl", ORDWR);
                      8: .B
                      9: write(ctlfd, "push async", 10);
                     10: .fi
                     11: .SH DESCRIPTION
                     12: .PP
                     13: This is not a device, but rather a
                     14: .I stream module
                     15: (see
                     16: .IR stream (3))
                     17: that can be pushed onto a stream.
                     18: This module provides the framing necessary to treat
                     19: a serial line as a Datakit trunk.
                     20: It is usually pushed onto a stream before the
                     21: .I dkmux
                     22: module.
                     23: The frame includes a CRC.
                     24: Any received frames with an incorrect CRC are
                     25: discarded.
                     26: .PP
                     27: The format of a message upstream of the module is:
                     28: .IP
                     29: channel # low byte
                     30: .br
                     31: channel # high byte
                     32: .br
                     33: control byte (0 means none)
                     34: .br
                     35: data bytes
                     36: .LP
                     37: The format of a frame is:
                     38: .IP
                     39: .B 0x7d        
                     40: .br
                     41: .B 0x7d
                     42: .br
                     43: channel # low byte
                     44: .br
                     45: channel # high byte
                     46: .br
                     47: crc low byte
                     48: .br
                     49: crc high byte
                     50: .br
                     51: .B 0x7d        
                     52: .br
                     53: .B 0x7d
                     54: .LP
                     55: All control bytes in the frame are preceded by a
                     56: .B 0x9d
                     57: byte.
                     58: All
                     59: .B 0x9d
                     60: and
                     61: .B 0x7d
                     62: bytes in the data are followed by a
                     63: .B 0x00
                     64: byte to distinguish them from framing or control
                     65: specifiers.
                     66: .SH "SEE ALSO"
                     67: .IR stream (3),
                     68: .IR cons (3),
                     69: .IR dk (3)
                     70: .SH SOURCE
                     71: .B /sys/src/9/port/stasync.c

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