berlinb@dvlmarv.uucp (Berlin Bedessee) (04/05/89)
Recently we have upgraded our inhouse system from a Microvax II to a Sun.
A compatibility problem we didn't forsee was the hookup to our LP25 printer.
The Sun comes with a typical Centronics (female DB25) interface and our
LP25 has some kind of DEC (female DB50) interface. I've obtained some
documentation pertaining to both, but there is still some information missing.
My goal is to fudge a cable so that I can get our LP25 to run on our Sun.
Here is basically all I have as far as documentation. This is simply the
pinouts for the both ends of the the interface. Following this
is my assumption for a fudged cable.
Pin Assignments for the Sun's Parallel Printer Port (DB25 Connector).
Pin # Signal Name
1 -STRB
2 D0
3 D1
4 D2
5 D3
6 D4
7 D5
8 D6
9 D7
10 -ACK
12 PE
13 SLCT
18 - 24 GND
Pin Assignments for LPV25 Printer (DB50 Connector).
Signal AMP AMP
Connector Connector
Signal Pin Signal Pin
READY 22 6
ON LINE 21 5
DEMAND 23 7
PARITY ERROR 27 11
DATA 1 19 3
DATA 2 20 4
DATA 3 1 2
DATA 4 41 40
DATA 5 34 18
DATA 6 43 42
DATA 7 36 35
DATA 8 28 44
PAPER INSTRUCTION 30 14
STROBE 38 37
BUFFER CLEAR 31 15
IDENT 0 50 32
IDENT 1 49 16
PARITY 29 13
+5V 12 --
TOP OF FORM 24 8
BOTTOM OF FORM 25 9
PAPER MOVING 26 10
PAPER MOVING 48 17
NOT VFU 47
VFU VERIFY RTN 33
INTERFACE CONNECTOR 46,45
VERIFY GROUND 39
My assumption for fudging a cable:
LP25 Printer (DB50) Sun (DB25)
DATA 1 ------------- D0
DATA 2 ------------- D1
DATA 3 ------------- D2
DATA 4 ------------- D3
DATA 5 ------------- D4
DATA 6 ------------- D5
DATA 7 ------------- D6
DATA 8 ------------- D7
STROBE ------------- -STRB
READY ------------- (PE)?
ON LINE ------------- SLCT
-ACK
The line between READY -- PE is only a guess!
Problems:
- Will the assumption (shown above) work!?
- I do not know the active logic levels for STROBE, READY, ON LINE, PE, and
SLCT, actually for most of them. If the logic levels are not compatible is
there still a non-active way to fudge this cable?
- What do I do with the -ACK signal? With normal Centronics interfaces this
is almost always used. Isn't it? I just can't seem to find a corresponding
line on the LP25.
- Basically I don't have any clear documentation as to the definition of the
LP25 lines. For example the line, DEMAND. Is this line asserted by the printer?
What does it do? What do the other lines do, if my assumption about them is
incorrect?
Can anyone help me with this problem? Does anyone have any information
pertaining to the DEC line definitions, or there active logic level?
Thanks in advance,
Berlinblarson@skat.usc.edu (Bob Larson) (04/05/89)
Apperently your printer has a standard dataproducts parrellel
interface. (The use 50 pin "winchester" connectors or db50, usually
the latter on newer devices.) A cable would not be enough to convert
to centronix parrellel, but the logic should be fairly simple. (A
latch and some miscelanious logic, strobe pulse generation, etc.
Depending on your printer, you may also have to decode control
characters to their individual signal lines for linefeed, formfeed,
etc.) More expensive, but easier, would be to buy a conversion box.
Black Box specializes in such oddities.
Bob Larson Arpa: Blarson@Ecla.Usc.Edu blarson@skat.usc.edu
Uucp: {sdcrdcf,cit-vax}!oberon!skat!blarson
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