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The multiplexer state contains these registers:
Name
Size
Radix
Symbolic
Action
STATE
310
Controller state
IBUF
16
8
Input buffer (from multiplexer to CPU)
OBUF
16
8
Output buffer (from CPU to multiplexer)
CMD
8
8
Command code
PARAM
16
8
Command parameter
PORT
8
10
Port number for last command
PORTKEY
8
10
Port key for last command
IOLEN
16
10
I/O transfer length for last command
UIEN
1
2
Unsolicited interrupts enabled
UIPORT
310
Unsolicited interrupt port
UICODE
310
Unsolicited interrupt reason code
KEYS [0:7]
8
10
Port keys, ports 0-7
PCONFIG [0:7]
16
8
Port configuration, ports 0-7
RCVTYPE [0:7]
16
2
Receive type, ports 0-7
CHARCNT [0:7]
16
8
Received character count, ports 0-7
TERMCNT [0:7]
16
8
Termination character count, ports 0-7
FLOWCNTL [0:7]
16
8
Flow control, ports 0-7
ENQCNTR [0:7]
7
10
ENQ character counter, ports 0-7
ACKWAIT [0:7]
10
10
ACK wait counter, ports 0-7
PFLAGS [0:7]
12
2
Port flags, ports 0-7
RBUF [0:7] [0:513]
8
8
Read buffers, ports 0-7
WBUF [0:7] [0:513]
8
8
Write buffers, ports 0-7
GET [0:7] [0:1]
10
10
Read/write get indexes, ports 0-7
SEP [0:7] [0:1]
10
10
Read/write separator indexes, ports 0-7
PUT [0:7] [0:1]
10
10
Read/write put indexes, ports 0-7
CTL
1
2
Control flip-flop
FLG
1
2
Flag flip-flop
FBF
1
2
Flag buffer flip-flop
The RBUF and WBUF registers logically represent eight character buffers of 514 bytes each, and the GET, SEP,
and PUT registers logically represent eight sets of two-word indexes. However, SCP supports only one-
dimensional register arrays, so they must be examined and deposited as linear arrays of 4112 bytes and 16 words,
respectively. So, for example, RBUF [0] is byte 0 of buffer 0, RBUF [513] is byte 513 of buffer 0, RBUF [514] is
byte 0 of buffer 1, etc.
The IBUF and OBUF registers default to octal display but may be displayed in single- or two-character formats by
specifying the
–A
or
–C
switch, respectively. Symbolic entry for these registers is also supported. The RBUF and
WBUF registers default to single-character format display and entry but may be overridden with numeric-format
switches, if desired.
