SNA IMF supports SNA Character String (SCS) control codes,
allowing certain HP printers to operate as LU.T1 (SCS mode) printers.
SNA IMF also supports the 3270 data stream, so HP printers can also
operate as LU.T3 (3270 mode) printers. Only one mode can be active
at a time. Printers in SCS mode use the EBCDIC character set and
dual case printing.
SCS control codes allow Pass Thru to call the TRAN3270 to emulate the following IBM 3287 printer keys:
These keys are used to communicate with the host application
program to suspend, resume, or cancel print operation.
The SCS data stream has fifty-six control codes. The IBM 3287
printer supports 18 of the SCS control codes, and HP printers support
17 of those 18 control codes. The Set Attribute (SA) SCS control
code is the only code supported by the IBM 3287 that HP printers
do not support. The SA control code is an extension of the SCS data
stream and is considered an option by IBM. Also considered optional
SCS extensions are the Structured Field and Attribute Processing
(SFAP) features. SNA IMF does not support these options.
Unsupported codes, if received, are rejected with sense code X'1003' (function not supported). Table B-1 “SCS Codes Emulated by Pass Thru” contains
a brief description of each SCS code supported by SNA IMF.
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 | NOTE: An LU.T1 session can support only a screen image of
3870 bytes and an RU size of 3584 bytes. If you exceed this RU limit,
the screen image will be overwritten. |
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For a complete description of the 17 supported SCS codes,
refer to the IBM 3287 Printer Models 1 and 2 Component
Description (IBM P/N GA26-3153).
SCS control codes and parameters can span request unit (RU) boundaries
within the same RU chain. However, if SCS control codes or parameters
span RU chains, the printer will stop processing SCS parameters
and send a negative response X'1005' (parameter error). Upon receipt of the first in
chain, it will return to SCS data processing.
As with the IBM 3287 printer, you must physically align paper
forms at the first line to be printed when you insert forms into
the printer. This action will ensure correct feeding of the forms.
Also, any change in format (SHF, SLD, SVF) must be followed by the
appropriate synchronizing function (CR, NL, FF) in order to maintain
format integrity.
Table B-1 “SCS Codes Emulated by Pass Thru” describes the SCS control codes
as emulated by Pass Thru.
Table B-1 SCS Codes Emulated by Pass Thru
SCS Code | EBCDIC (hex) | SCS Name | Pass Thru's Action |
|---|
CR | 0D | Carriage Return | Moves the print position horizontally
to the left margin on the same line. If the print position is already
at the left margin, then Pass Thru does nothing. |
| LF | 25 | Line Feed | Moves the print position vertically down to
the next line. |
NL | 15 | New Line | Moves the print position horizontally to the
left margin and vertically down to the next line. |
BS | 16 | Back Space | Moves the print position horizontally
one position to the left without regard to the left margin. If the
print position is already at column one, then Pass Thru does nothing. |
FF | 0C | Form Feed | Moves the print position to the top left
margin of the next form. If the maximum print position has not been
set, a default value of one is used, and the print position moves
to the left margin of the next line. |
HT | 05 | Horizontal Tab | Moves the print position horizontally,
from left to right, to the next tab stop. A space is printed if
there are no horizontal tab stops set to the right of the current
print position. If the maximum print position has been passed, a
New Line is performed. |
VT | 0B | Vertical Tab | Moves the print position vertically down
to the next vertical tab stop. A line feed is printed if there are
no vertical tab stops below the current print position. If the bottom
margin has been passed, a Form Feed is performed. |
| SHF | 2BC1 | Set Horizontal Format | Sets the maximum print position, left
margin, right margin, and horizontal tab stops. The format of the parameters
and the defaults are the same as those specified in the IBM
3287 Printer Models 1 and 2 Component Description. |
SVF | 2BC2 | Set Vertical Format | Sets the maximum print line, top margin,
bottom margin, and vertical tab stops. The format of the parameters
and defaults are the same as those specified in the IBM
3287 Printer Models 1 and 2 Component Description. |
SLD | 2BC6 | Set Line Density | The emulator accepts this code, but performs
no function. The default density of 6 LPI is always used. An IBM
3287 allows densities of 3, 4, 6, or 8 LPI. |
VCS | 04nn | Vertical Channel Select | Causes a Line Feed to be performed. This
is the same operation an IBM 3287 performs. The IBM 3287 does not
support skipping using the VCS code. |
TRN | 35 | Transparent | Provides for transmitting
data in transparent mode. Transparent data is not checked for SCS
codes. The print position moves one character position as each data
byte is interpreted. Valid graphics are printed and invalid graphics
are printed as hyphens (-). (Invalid graphics are identified by
hyphens in the IBM 3287 Printer Models 1 and 2 Component Description.) |
Note that the first byte following the
TRN code is a binary value defining the number of bytes of transparent
data to follow. This length does not include the length byte. |
IRS | 1E | Interchange Record Separator | Causes a New Line to be performed. This
response is identical to the response of an IBM 3287 printer. |
BEL | 2F | Bell | The emulator accepts this code but performs
no function. An IBM 3287 rings the bell. |
INP | 24 | Inhibit Presentation | The emulator accepts this code, but performs
no function. This response is identical to the response of an IBM
3287 printer. |
ENP | 14 | Enable Presentation | he emulator accepts this code, but performs
no function. This response is identical to the response of an IBM
3287 printer. |
GE | 08nn | Graphics Escape | Causes a hyphen to be printed for the
graphics escape character. The character that follows the graphics escape
character is printed using the base character set. This is identical
to what the IBM 3287 does when the APL Text feature is not installed. |
