Model 100 Hints and Tips				    Page 1


The following is a series of "hints and tricks" for getting the
most out of the TRS-80 Model 100.

This file is intended to become an ongoing 'mini-magazine'
within this SIG.  Plans for future updates include deciphering
some ROM code for use within BASIC and Machine Language
programs.


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o	"Printer Not Ready"

There is a problem within the TRS-80 Model 100 that makes the 
machine seem to "hang".  This is usually caused by pressing the
PRINT key, which attempts to copy the contents of the non-
graphic Model 100 screen to an attached printer.  The problem 
manifests itself if there is no printer attached.

Additionally, this can be caused by a BASIC or Machine Language
(M/L) program, or one of the ROM programs TEXT, TELCOM, SCHEDL,
and ADDRSS attempting to output to a non-existant printer.

Usually, pressing SHIFT-BREAK will produce an "aborted" message
within a ROM program, or "?IO Error" within a BASIC program.  
If a machine language program is executing and the (non-
documented) error vector is not 'plugged', an "?IO Error" will 
be generated and a return will be made to BASIC.

Disabling the PRINT key is touchy at best.  Actually, it is 
possible to disable the key, and all the 'miniature' keys 
immediately underneath the display (F1-F8, PASTE, LABEL, PAUSE/
BREAK, etc.).  In my opinion, though, the loss of the function 
keys is greater than the problem of the PRINT key.

Since there is no easy, '1-poke' method of totazlly disabling 
the printer in the Model 100, we must be satisfied with the 
"?IO Error" in BASIC (unless it is trapped with an ON ERROR 
statement).  On the other hand, there is a simple way in 
Machine Language or BASIC to tell if there is a printer 
attached.


Model 100 Hints and Tips				    Page 2


BASIC

IF (INP(187)AND6)<>2 THEN PRINT"Not Ready"


Z80 Assembly Language:

	PUSH	BC		;Save BC
	LD	B,A		;Save A Reg
	IN	A,(0BBH)	;Get printer status
	AND	06H		;Mask off non-status
	XOR	02H		;Set flag bits
	LD	A,B		;Restore A Reg
	POP	BC		;Restore BC
	JP	NZ,NOTRDY	;Not ready if Non-Zero
	...			;Printer Ready if code falls
				;through



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o	The PASTE buffer has been documented by more than one 
program (although NOT by Radio Shack!) to reside at the address
at F88CH-F88DH (63628-63629 decimal).  This address is stored 
in typical 8080 LSB/MSB format.  What isn't so well documented 
is that the two bytes preceding that address F88A-F88BH (63630-
63631 decimal) contain the pointer to the text returned by 
pressing the SHIFT and PRINT keys simultaneously.  (In BASIC, 
SHIFT-PRINT points to the text "llist" followed by a carriage 
return in ROM... try it!)  Both of these "buffers" are 
terminated by a null byte, or CHR$(0).  The SHIFT-PRINT key can
thus be useful in both BASIC and Machine Language programs.


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o	"Carrier Detect in Basic"

	A useful routine has been uploaded to the SIG called 
DIALER.100 and was submitted by Jerry Kohl [71256,23].  It is 
heavily commented and explains a useful application of a 
routine that "times out" if carrier is not detected within a 
given amount of time.  The routine also contains an npublished
entry point to TERM mode within TELCOM without losing carrier.

Model 100 Hints and Tips				    Page 3


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o	Tandy BUG Department:

	The CHKDC ROM Call documented by Tandy at 5AA9H 
contains a "small" bug.  It seems that the routine was actually
written for the ADRSS and SCHEDL ROM programs to search for 
ADRS.DO and NOTE.DO.  The limitation here is that the routine 
will only work if the filename being searched for contains 4 
characters or less in the file name (preceding the required
".").

	How to get around this problem:

	The solution is really quite simple, just load the A 
register with 10 (Hex 0A) and enter the routine at the addess 
5AABH.


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o	What is the Shack up to next?

	I have heard from more than one source that the price 
cut we saw on the Model 100 a couple of months ago is going to 
be repeated sometime at the end of March or beginning of April.




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o	BREAK key disable

	Disabling the BREAK key can be accomplished by POKEing 
a value of 128 into the reserved RAM location 63056 (Hex F650).
  This effectively eliminates all of the top row of keys
(function keys, etc.).  To re-enable, just POKE the value 0
back into the same location.



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That's all for now... next installment should be available 
shortly.


Send comments and/or suggestions to larry gensch via CompuServe
EMAIL or through the Model 100 SIG.

		larry gensch
		[72236,3516]
		03/21/84