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ADM3.MOD
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Text File
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1984-04-29
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4KB
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84 lines
LEAR SIEGLER ADM3 MODIFICATIONS
ONE OF THE MORE POPULAR COMPUTER TERMINALS, WHICH IS BEING USED BY
THE COMPUTER HOBBYEST, IS THE LEAR SIEGLER ADM3 OR ADM3A. HOWEVER, THERE ARE
SPECIAL PROBLEMS WHEN THEY ARE USED WITH CP/M, BUT THESE PROBLEMS CAN BE
VERY EASILY MODIFIED BY TWO SIMPLE MODS THAT I HAVE DEVELOPED. THESE MODS
CAN BE EASILY INSTALLED AND REMOVED, AND DO NOT REQUIRE SOLDERING. THEY TAKE
ABOUT 15 MINUTES TO INSTALL AND DON'T EVEN REQUIRE THE MOTHER BOARD TO BE
REMOVED. UNFORTUNATELY, MY MOD ONLY APPLIES TO THE ADM3, BUT I IMAGINE THAT
THE ADM3A CIRCUITRY IS SUFFICIENTLY SIMILAR THAT THE MODS CAN BE IMPLEMENTED.
MOD #1-----THE PROBLEM:THE CP/M EDITOR AND FDOS PREEMPTS THE CHARACTER
CONTROL Z FOR VARIOUS PURPOSES. IMSAI RECOMMENDS THAT THE
BLANK SCREEN CAPABILITY OF THE ADM3(WHICH USES CONTROL Z) BE
DISABLED. THIS IS UNFORTUNATE BECAUSE THE BLANK SCREEN
CAPABILITY IS HANDY TO USE IN GAMES AND OTHER APPLICATIONS.
THE SOLUTION:CONVERT THE ADM3 'BLANK SCREEN' SIGNAL FROM CONTROL
Z TO CONTROL Y. THIS ENABLES YOU TO USE THE BASIC STATEMENT
'PRINT CHR$(25)' TO CLEAR THE SCREEN
PROCEDURE: 0.TURN OFF THE POWER
1.PREPARE A 3 INCH STRAND OF INSULATED WIRE WRAP WIRE
BY STRIPPING ONE END FOR 1/4 INCH AND THE OTHER 1/2 IN
2.REMOVE THE I.C. #J2 FROM ITS SOCKET AND BEND PIN #10
90 DEGREES(SO IT WONT INSERT IN THE SOCKET). REPLACE
THIS I.C. IN ITS SOCKET.
3.REMOVE I.C. #L3 AND PLACE THE 1/4 STRIPPED END IN
THE PIN #2 HOLE. REINSERT THIS I.C.
4.TWIST THE 1/2 INCH END OF THE WIRE AROUND I.C. J2
PIN 10 SEVERAL TIMES USING NEEDLE NOSE PLIERS.
5.REACTIVATE THE CLEAR SCREEN FUCTION USING THE DIP
SWITCH ON THE REAR OF THE MOTHER BOARD.
MOD#2-----THE PROBLEM: NOTHING IS MORE FRUSTRATING TO ME THAN TO GET COMPILER
ERROR MESSAGES WHEN I HAVE INADVERTANTLY INSERTED A CONTROL
CHARACTER IN A STATEMENT. THE DIFFICULTY IS THAT THESE CONTROL
CHARACTERS DO NOT PRINT ON THE SCREEN AND I HAVE NO WAY OF
KNOWING THAT THEY ARE THERE. A SIMILAR PROBLEM OCURRS WHEN
SOMEONE HAS INSERTED CONTROL K (FOR FORMFEED), OR OTHER
CONTROL CHARACTERS, IN A TEXT AND I WANT TO MOVE OR REMOVE IT.
THE SOLUTION: IF YOUR TERMINAL HAS LOWER CASE CAPABILITY, THEN YOUR
ROM HAS THE CONTROL CHARACTERS BURNT INTO IT.
PROCEDURE: 1.PREPARE A 1+1/2 INCH WIRE BY STRIPPING ONE
END FOR 1/2 INCH AND THE OTHER FOR 1/4 IN.
2.REMOVE IC.#F3 AND BEND PIN 12 FOR 90 DEGREES.
3.PLACE THE 1/4 INCH WIRE END IN THE HOLE FOR
PIN 7 AND REINSERT THE I.C. #F3.
4.WRAP THE 1/2 INCH END AROUND PIN 12.
5.SET THE DIP SWITCH ON THE REAR OF THE MOTHER
BOARD TO U/L DISPLAY
DIFFICULTIES: THE LINE FEED CHARACTER WILL DISPLAY AND
THEREFORE EFFECTIVELY REDUCE THE LINE LENGTH
FROM 80 TO 78 CHARACTERS.
THE BACKSPACE (CONTROL H) NO LONGER WORKS
PROPERLY SINCE THE TERMINAL NOW CONSIDERS
CONTROL H AS A VALID CHARACTER AND ATTEMPTS
TO ADVANCE THE CURSOR WHILE BACKSPACING IT.
SUGGESTION: USE A SPDT SWITCH FOR THIS MOD SO THAT YOU
NEED ONLY DISPLAY CONTROL CHARACTERS WHEN YOU
DESIRE.
SINCE MANY PEOPLE ARE USING THE ADM3A, I'LL DESCRIBE THESE MODS IN
TERMS OF CIRCUIT CHANGES.
MOD#1 BEFORE MODIFICATION THE 3 NEGATIVE INPUT 'AND' GATE #J2 (7427) SENSES
THE THREE SIGNALS 'NOT COLUMN 1','NOT DATA 4',AND 'NOT XX2'. THIS MOD
CHANGES THE LATTER SIGNAL TO 'NOT XX1'. 'NOT XX1' IS OBTAINED FROM
THE 7442 DECODER #L3.
MOD#2 BEFORE MODIFICATION THE 4 NEGATIVE INPUT 'AND' GATE #F3 (7425) WHICH
IS USED TO CREATE THE SIGNAL 'FORESPACE' AND WHICH IN TURN IS USED TO
CREATE THE INCREMENT CURSOR SIGNAL,USES THE FOLLOWING SIGNALS
'NOT CC80','CTRL CHAR','DEL',AND 'DOIT'. THIS MOD SETS THE 'CTRL
CHAR' INPUT TO LOW BY GROUNDING PIN #12. THIS RESULTS IN THE CONTROL
CHARACTERS BEING PLACED IN MEMORY AND DISPLAYED JUST AS ANY OTHER
OTHER CHARACTER (PROVIDING THE LOWER CASE PROM IS PRESENT).
CONTRIBUTED BY R.A.GREGOIRE, RD10,CARLISLE,PA