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PROTOCOL CONVERTER A/S-2G
16
In 3741 protocol, each block contains only one record. If SW3, Switch #5 is OFF, the A/S-2G will fill
the block with spaces until it reaches 128 characters . If SW3, Switch #5 is ON, the block will end
immediately after CR.
NOTE:
• If SW3, Switch #3 is OFF, then one character of the total count must be allotted to the CR. The CR
will be translated into EBCDIC as a NL (New Line). Thus, if block size is specified as 80 characters,
79 characters plus the CR would make a full 80 character record. Entering 80-characters and a CR
would cause 2 records to be sent: one with the 80 characters; the second with the NL character and,
if SW3, Switch #5 is OFF, 79 spaces.
• When SW3, Switch #3 is ON, the A/S-2G will delete CR from the character count and send no
representation of the CR with the EBCDIC data.
4.1.5 USE OF CARRIAGE RETURN
(
A) 2770/2780 MODE
Data from the asynchronous device is buffered (stored in RAM) until a CR (ASCII 0D Hex) is entered.
If the A/S-2G receives asynchronous characters up to the selected block size without receiving a CR
character, the A/S-2G will add an IUS character and a 2-byte CRC sequence to the block.
When the A/S-2G receives a CR, the A/S-2G sends any buffered data to the synchronous device with
an ETB (EBCDIC Hex 26).
The last block of asynchronous data must end with a “Control D” (ASCII Hex 04). The A/S-2G will
send the block, adding with an ETX (EBCDIC Hex 03). After receiving a positive acknowledgement,
the A/S-2G sends an EOT.
(
B) 3741/3780 MODE
Data from the asynchronous device is buffered until a CR (ASCII 0D Hex) is entered. When the
A/S-2G receives a CR, the A/S-2G inserts an IRS (EBCDIC 1E Hex). Data will continue to accumulate
until the selected block size is exceeded. At this point, the A/S-2G sends the full block of data.
The last block of asynchronous data must end with a “Control D” (ASCII Hex 04). The A/S-2G will
send the block, adding with an ETX (EBCDIC Hex 03). After receiving a positive acknowledgement,
the A/S-2G sends an EOT.
4.1.6 FLOW CONTROL
The input buffer (RAM) is capable of storing up to 1720 characters. The asynchronous device can
continuously send data to the A/S-2G if RAM is available and the character string contains a CR code
before the buffer fills. (However, the maximum block size that is acceptable to the synchronous device
must be considered.)
ASCII CHARACTERS NOT TRANSLATED TO EBCDIC
CR (Carriage Return) when SW3, Switch #3 is ON, LF (Line Feed), Control characters are not passed.
Character Hex Character Hex
NUL 00 ACK 06
SOH 01 DLE 10
STX 02 NAK 15
ETX 03 SYN 16
EOT 04 ETB 17
ENQ 05 US 1F
Table 4-2. ASCII characters not translated to EBCDIC.