Black Box PROTOCOL CONVERTER A/S-4 - Manual (Page 58)

CHAPTER 8: Batch Operation
57
When sending data to the printer each character is inspected and then sent if needed. A column count
is kept to determine the position of the printer’s print head which is compared to the selected column
width of the paper. If a space character is found, it is not sent right away to the printer. The following
characters are checked and if no other character other than a space is present in the line, a CR LF or CR
LF LF (Double spacing) is sent to the printer disregarding the received spaces.
The SNA host can send transparent data to the printer. Most of the time this EBCDIC data is converted
into ASCII because transparence is generated by the application (e.g. JES, POWER) which looks for a
character less than an EBCDIC space (x’40’) in value, if this character is found, the print line is sent in
transparent form. Usually the character causing this is a null (X’00’) inserted in a JOB name or ROOM
number because no value was assigned. If the actual SNA data received from the host needs to be
printed, the first two data characters must be a transparent indicator (TRN X ‘35’) followed by the
number of transparent characters in hexadecimal. Example message received from SNA host:
TRN # TRN # data —> 1st TRN # generated by JES 2nd TRN # generated by program
The printer can be connected to the A/S-4 in many ways as mentioned below:
1. Printer directly connected to the terminal port with a single cable. In this configuration no
VDU is present. The host must do an Auto-BIND to connect the A/S-4 to he application (e.g.
JES2, CICS) or use the Auto Logon function of the unit. With a single device, only one LU is
needed but both may be used. Normally the VDU LU is the LU used when running with a
single LU. The host must start the print job since no VDU is present. Hardware throttle
(must have CTS before sending data) or software throttle (XON/OFF protocol) may be used
to control the rate of data going to the printer.
2. Printer attached to a VDU’s auxiliary/printer port where the VDU is directly connected to the
terminal port of the A/S-4. This mode of operation allows the VDU to run at a faster baud
rate than it’s attached printer. Having two LUs active, one for inbound (to host) data and an
outbound (from host) LU will increase the speed of the printer and also allow the VDU to
start or stop jobs, interrupt the printer or allow a card device to send a job in to the host while
a job is being printed. Software or hardware throttle is supported.
3. Printer attached with the special “Y” VDU/Printer cable. The VDU and printer must run at
the same baud rate in this setup and hardware throttle is the only way to control the flow of
data to the printer (XON/OFF not supported). When using the “Y” cable, the VDU will be
able to receive data while the printer is off-line, replacing paper or throttling. This
configuration is very similar to item 2 with two LUs active which allows the VDU to control the
printer. In this mode the VDU (PC or computer) can go off-line and run applications while
the printer is receiving data from the SNA host, as long as the VDU supplies Data Terminal
Ready (DTR) pin 20 to the A/S-4.