serial buffer: handshake jumper settings??

[sebugg@presby.edu (Stephen Buggie)]

sebugg@presby.edu                                            August 8, 1993

         QUADRAM "MICROFAZER" SERIAL-TO-SERIAL PRINTER BUFFER:
       ADVICE SOUGHT REGARDING SETTING OF "HANDSHAKING" JUMPERS
       ========================================================

       I have several printers, but my favorite is a NEC Spinwriter 7715, a
high speed (55 cps) letter quality (thimble impact) serial printer.  This
printer was new in 1981, and it is built for heavy duty usage.  It is now
connected to my Apple Super Serial Card, and the data are sent at the rate
of 600 baud from the serial card to the printer.  If data are sent at a
faster rate (e.g., 1200 baud), the printer does o.k. with a partial page
but jams up near the bottom of a full page.  But it performs well at the
600 baud data rate, running at its maximum 55cps print rate.

       Recently I bought a used serial-to-serial 64K print buffer: a
Microfazer by Quadram Corp.  It is in excellent condition and I have the
docs for it.  I seek advice on setting its "handshaking jumpers" since
my first attempt to set them did not succeed.

       The dip-switch settings and the terminal/modem block on the super
serial card are set correctly.  When the serial card is connected directly
to the printer, they work well together, printing accurately and at the
printer's maximum rate.

       The following internal jumper settings must be done on the Microfazer.
First, the baud rate can be set by jumpers separately for the input
from the serial card, and for the output to the printer.  The super serial
card can send data as fast as 19,200 baud, and the microfazer input or
output can go that fast also.  Later, I will set the buffer input jumper
to a fast transmission rate (eg, 19200 baud) so that the computer will be
freed quickly for other work.  For now, I have set the jumpers for input
and also for output to the 600 baud rate that I know the printer can handle.

       My confusion concerns the setting of the "handshaking jumpers" because
the manual's explanation is unclear to me.  The manual explains it with a
few paragraphs, which follow.  There are two blocks of jumpers, with two
connectors each:

COMPUTER INTERFACE                      PRINTER INTERFACE
HANDSHAKE JUMPERS                       HANDSHAKE JUMPERS
(data from computer                     (data from buffer
    to buffer)                              to printer)
-------------------                     -----------------

    ______                                  ______
   |  ..  |  DSR                           |  ..  | DTR
   |      |                                |      |
   |  ..  |  CTS                           |  ..  | RTS
   |      |                                |      |
   |  ..  |  RTS                           |  ..  | CTS
   |      |                                |      |
   |  ..  |  DTR                           |  ..  | DSR
   |______|                                |______|

       The following paragraphs are quoted directly from the Microfazer
manual:
______________________________________________________________________________
"The computer interface handshake signals must be selected.  Two jumpers are
provided for selecting which handshake lines are to be used. Selection is made
by placing the jumpers across the appropriate pair of pins."

"The Microfazer uses either the DTR or RTS signals to indicate its readiness
to accept data from the computer.  The Microfazer's DTR signal connects to
the computer's DSR input, while the Microfazer's RTS signal connects to the
computer's CTS input.  Most computers will monitor their serial port's CTS
line to determine if the connected piece of equipment is ready to accept data.
Thus, to signal the Microfazer's readiness at the computer's CTS input, the
Microfazer's RTS line must be selected by plugging the jumpers across the
RTS pair of pins."

"However, to signal the Microfazer's readiness to accept data via the DSR
input, the DTR pins must be jumpered."

"If RTS is selected as the Ready indicator, the DTR output will, by default,
appear active all the time.  By the same token, if DTR is selected, the RTS
output will appear active all the time.  And in caseswhere neither is selected,
both will appear active all the time."

"To determine the computer's request for clearance to send data, DSR or CTS
can be used.  CTS on the Microfazer connects to RTS on the computer, and
DSR on the Microfazer connects to DTR at the computer.  If your computer
uses its RTS line to request clearance to send, the CTS option should be
selected;  if it uses DTR, the DSR option should be selected.  DSR or CTS
is selected by plugging a jumper across the corresponding DSR or CTS lines.
In cases where neither is selected (by not installing the plug, the Microfazer
will see DSR and CTS as being active all the time."

"The PRINTER handshake signals are set in an identical manner.  But while the
pairing of printer handshake signals --- RTS/DTR;  CTS/DSR ---  is the same,
the use of these signals is slightly different."

"The Microfazer can sense the printer's "ready" signal on either its DTR or
RTS input lines.  A printer that is configured as DTE usually uses the DTR
line to signal its readiness.  The appropriate signal must be selected by
plugging a jumper across the DTR or RTS pins (in the printer group).  If
neither signal is jumpered, the Microfazer will see the printer as ready all
the time.  In cases where neither is selected, the Microfazer will see the DTR
and RTS as being active all the time."

"CTS or DSR may be selected to indicate that the Microfazer is powered up and
ready to send data to the printer.  Some printers may need to have CTS or
DSR active before they will look for incoming data.  To see if either of
these signals is needed, consult your printer's manual.  [Buggie's note:
I found not mention of this in my NEC printer's manual.]  The appropriate
signal may be selected by plugging the jumper across the appropriate pins.
In cases where neither is selected, both signals will appear active to the
printer all the time.  In most cases, the printer does not need either
signal."
_____________________________________________________________________________

       I hope that someone will advise me on how to set the jumpers!  There
are two jumpers for input to be set among four inputs (DSR,  CTS,  RTS,  DTR),
and also two jumpers to be set among four outputs (DTR,  RTS,  CTS,  DSR).
There are so many possible settings that discovering them via trial-and-error
seems hopelessly tedious.   Assistance will be appreciated!

Stephen Buggie             sebugg@presby.edu

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 ** Stephen Buggie  Psych Dept  Presbyterian College   Clinton SC 29325 **
 ** sebugg@presby.edu                 voice: (803) 833-8337 or 833-1632 **
 **             The Apple II pledge:  never to mess with MS-DOS         **
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