Asynchronous Terminals and Printer Processes Programming Manual

PRINTER PROGRAMMING CONSIDERATIONS
Loading the DAVFU
S5004–048
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
111111
0000
Channel 0
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 11
Channel 10
Channel 9
Channel 8
Channel 7
Channel 6
Figure 7-1. DAVFU Buffer Word Format
For example, %37400 (default for line 31) indicates that channel
stops are to be set for channels 2, 3, 4, 5, 6, and 7.
Exactly one channel 0 (top of form) stop must be defined in the
VFU buffer, and at least one stop must be defined for each of the
other VFU channels. File-system error 105 (VFU ERROR) occurs if
you attempt to load an invalid VFU buffer.
The number of words in the VFU buffer determines the form
length. The maximum length allowed is 254 lines (508 bytes in
the buffer). If the byte count specified in a DAVFU load exceeds
this maximum, or if it is not an even number, file-system error
21 (ILLEGAL COUNT) is returned.
Use channel 0 to indicate which line the printer should skip to
if CONTROL 1, parameter = 0 is issued or if the operator presses
the TOP OF FORM button on the printer. Use channel 2 for line
termination when spacing and perforation skip are enabled. Use
channel 11 to indicate which line the printer should skip to if
CONTROL 1, parameter = 11 is issued and also to indicate when
paper out should be reported.
If single spacing and automatic perforation skip are required,
the DAVFU should contain a stop in channel 2 for lines 1 through
60. The I/O software does not use the DAVFU for single spacing
without automatic perforation skip.
When the printer runs out of paper, it waits until the current
page has been printed before reporting the condition to the
application program.
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