🚀 go-pugleaf

In article <4366@vidiot.UUCP>, brown@vidiot.UUCP (Vidiot) wrote:
> 
> In article <28OCT199212320113@comb1.comb.umd.edu> jeffc@comb1.comb.umd.edu (Jeff Clowser; IRG) writes:
> <
> <uh, I happen to have a Personal Laserwriter NT, configured as a serial printer,
> <9600bd,8,N,1, XON/XOFF, binary postscript, so I know it works.  In fact, that
> <is one of the default settings for this printer.  It shows how to set it up
> <(more or less) in the appendices of the printer manual.
> 
> As someone else points out, this mode makes you lose the ^T and ^D functions
> of the printer.  The ^D function is a must for telling the printer end-of-job.
> It comes is very handy when killing a job.
> 
> I therefore prefer hex encoded data, not real binary.  Too dangerous.
> 
> <BTW - There is no such thing as a parallel port on a PLW NT...
> 
> The LaserWriter II NT doesn't have one either. :-(
> -- 
>       harvard\                          spool.cs.wisc.edu!astroatc!vidiot!brown
> Vidiot  ucbvax!uwvax..........!astroatc!vidiot!brown
>       rutgers/            INTERNET:vidiot!brown%astroatc.UUCP@spool.cs.wisc.edu
>                                    brown@wi.extrel.com

I tried posting this before....

Here are the definitions:

Raw: Lets all data pass through unfiltered. Control characters such as
End-of-file (CTRL-D) and status queries (CTRL-T) or passed through and not
acted upon.

Normal: Data passing through is filtered. Control characters perform their
intended function. Status queries (CTRL-T) will have a status returned;
End-of-file (CTRL-D) characters will end print job.

Binary: We took the following from pages 15 to 17 of the "LaserWriter IIf
and LaserWriter IIg Printers Developer Note" (APDA R0230LL/A):

Binary serial protocol

LaserWriter printers support an alternate protocol for the serial
communication channels. While this protocol allows all character codes to
be transmitted as data, it also allows certain characters to be used for
specifying control functions, which may be handled asynchronously by the
communications driver. Those control functions include requesting status,
aborting a job, marking ends of jobs, and controlling flow for the serial
channels.

Because this protocol can transmit any character code, it can be used for
sending PostScript language jobs that contain binary images or for sending
commands with any sequence of control characters to emulators.

Because this protocol can be used for sending both PostScript language
programs and emulation jobs, it provides a way of switching between the
PostScript interpreter and the emulators without flushing the input
buffers. The manner of switching between PostScript language programs and
emulations is described in Chapter 3 of the "LaserWriter Reference".

To select the binary serial protocol, set the operating mode switch to
position 6, or use the LaserWriter Utility to set one of the changeable
parameter sets to use binary protocol.

The binary serial protocol requires the host computer to insert a quoting
character at certain places in the data stream and to modify the character
codes for certain characters. (This procedure is described later in this
section.) That means that the host computer must filter the data before
sending it to the printer. The filtering may be done by an application
program or within the operating system of the host computer.

When the binary serial protocol is enabled, it operates on communications
in both directions. Therefore, the host computer must also filter any data
it receives from the printer.

There are eight control characters that are treated as control functions
rather than as data when they are received by the communications driver.
The control characters are defined in Table 2-1.

Table 2-1  Control characters in the binary serial protocol

Hex value    ASCII name    ASCII function    Control function

01           SOH           CTL-A             Quote data byte
03           ETX           CTL-C             Abort job and flush to end of
file
04           EOT           CTL-D             End-of-job marker
05           ENQ           CTL-E             None
11           DC1           CTL-Q             XON in XON/XOFF flow control
13           DC3           CTL-S             XOFF in XON/XOFF flow control
14           DC4           CTL-T             Request printer status
1C           FS            CTL-\             None

To transmit these characters as data, they must be quoted, as follows. To
quote a character, the program replaces the character with the
two-character sequence consisting of CTL-A followed by the result of the
exclusive-OR (XOR) of the character to be transmitted with $40 (the dollar
sign indicates hexadecimal). For example, to send a byte with the value
$14, a program must send the 2-byte sequence $01$54. This method of quoting
guarantees that whenever any of the eight special characters is received,
the control function is intended, regardless of whether the preceding
character is a CTL-A. Because of that character independence, the
generation and processing of asynchronous
control characters can take place at a lower level than the generation and
consumption of the data stream. In particular, on the host computer, the
CTL-A quoting convention can be implemented by a user program while
XON/XOFF processing is performed independently by the operating system.

All byte values other than those of the eight special characters are
transmitted by simply sending the value.

After a CTL-A is received, the next character received that is not one of
the eight special characters must be the result of XORing one of the
special characters with S40. The reception of any other character
constitutes an error in the input data. Between the CTL-A and the XORed
character, any number of special characters may appear, except for the
special characters that are handled synchronouslyQCTL-A and CTL-D.
Reception of CTL-A or CTL-D between a CTL-A and the XORed character
constitutes an error.

When one of the special characters arrives unquoted and it specifies no
control function for the channel, the character is discarded. For example,
if XON or XOFF is received and XON/XOFF flow control is not in use, the XON
or XOFF character is discarded. The characters CTL-E and CTL-\ currently do
not specify any control functions. They are included among the characters
that must be quoted
future.

The binary serial protocol is different from the simple serial protocol in
that there is no mapping between end-of-line conventions with the binary
protocol. Whatever end-of-line character (<CR>, <LF>, or <CR><LF>) is sent
by the host is received by the interpreter or emulator in the printer. The
PostScript interpreter handles different end-of-line characters in a
uniform way, but a program that reads data (by means of a read or
readstring operator) receives whatever characters were sent by the host.
Likewise, whatever output is generated by a PostScript program (by means of
a print or = operator) is sent
unchanged.

Note: The standard end-of-line character in the PostScript language,
corresponding to '\n' in a PostScript language string, is <LF>.

Scott Winders
winders@aux.support.apple.com

"My opinions are my own, not my employer's"