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1.
The DEF 4 instruction sets the character buffer to the transmit mode.
2.
The transmit clock sends data onto the line at regular intervals.
3.
When the transmit buffer shift register, becomes empty the data contained in the data
register is transferred to the shift register.
4.
This is the binary representation of the character in the shift register.
5.
Line 5 shows the output of the transmit section of the character buffer.
6.
The transmit flag is shown setting when the word is transferred from the data register
to the shift register.
The example below shows one method that might be used to receive characters from a character
buffer.
LOOK
INPUT
EOM
..QEE
ORG
DEF
NES
BZE
TRA
STB
ADO
XBZ
BNZ
IND
OCT
012erand
7000
31
1
·k-1
R,B
INPUT
INPUT
EOM
LOOK
1000
000077
x
Remarks
SET RECEIVE MODE, RESET FIAG AND
BUFFER
RECEIVE FIAG SET?
NO, GO BACK
YES, TRANSFER CHARACTER TO B
x
STORE IN MEMORY
ADD ONE TO INPUT ADDRESS
IS THIS THE END OF MESSAGE?
NO, GO GET ANOTHER CHARACTER
INPUT ADDRESS
END-OF-MESSAGE CHARACTER
1.
The DEF 3 1 instruction puts the character buffer into the receive mode and resets
the receive flag and data buffer.
2.
The NES 1 command tests the receive flag for a,set condition.
3.
When the flag sets, the BZE testfails and the character is transferred to the B-register.
4.
The character is stored in memory and tested to see if it is an end-of-message character.
5.
If
the character isn't an EOM, control is transferred back to get next character.
Word Buffer Channel (WBC)
The word buffer channel (WBC) provides the interface to a half-duplex transmission line, on a
word basis.
A WBC buffers a bit stream 20 bits in length, where the length is determined by
the wiring in the 20-bit code level connector.
[ID&lf&~[Elf CJ~@------------
V-25
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