330 lines
17 KiB
Plaintext
330 lines
17 KiB
Plaintext
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Model 100 Hints and Tips
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The following is a series of "hints and tricks" for getting the most out of the TRS-80 Model 100.
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This file is intended to become an ongoing 'mini-magazine' within this SIG. Plans for future updates include
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deciphering some ROM code for use within BASIC and Machine Language programs.
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_____________________________________________________________________________________________________________________
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* "Printer Not Ready"
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There is a problem within the TRS-80 Model 100 that makes the machine seem to "hang". This is usually caused by pressing
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the PRINT key, which attempts to copy the contents of the non-graphic Model 100 screen to an attached printer. The problem
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manifests itself if there is no printer attached.
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Additionally, this can be caused by a BASIC or Machine Language (M/L) program, or one of the ROM programs TEXT, TELCOM,
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SCHEDL, and ADDRSS attempting to output to a non-existant printer.
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Usually, pressing SHIFT-BREAK will produce an "aborted" message within a ROM program, or "?IO Error" within a BASIC
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program. If a machine language program is executing and the (non-documented) error vector is not 'plugged', an "?IO Error"
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will be generated and a return will be made to BASIC.
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Disabling the PRINT key is touchy at best. Actually, it is possible to disable the key, and all the 'miniature' keys
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immediately underneath the display (F1-F8, PASTE, LABEL, PAUSE/ BREAK, etc.). In my opinion, though, the loss of the
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function keys is greater than the problem of the PRINT key.
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Since there is no easy, '1-poke' method of totazlly disabling the printer in the Model 100, we must be satisfied with the
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"?IO Error" in BASIC (unless it is trapped with an ON ERROR statement). On the other hand, there is a simple way in
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Machine Language or BASIC to tell if there is a printer attached.
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BASIC
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IF (INP(187)AND6)<>2 THEN PRINT"Not Ready"
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Z80 Assembly Language:
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PUSH BC ;Save BC
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LD B,A ;Save A Reg
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IN A,(0BBH) ;Get printer status
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AND 06H ;Mask off non-status
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XOR 02H ;Set flag bits
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LD A,B ;Restore A Reg
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POP BC ;Restore BC
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JP NZ,NOTRDY ;Not ready if Non-Zero ...
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;Printer Ready if code falls
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;through
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_____________________________________________________________________________________________________________________
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The PASTE buffer has been documented by more than one program (although NOT by Radio Shack!) to reside at the address at
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F88CH-F88DH (63628-63629 decimal). This address is stored in typical 8080 LSB/MSB format. What isn't so well documented is
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that the two bytes preceding that address F88A-F88BH (63630-63631 decimal) contain the pointer to the text returned by
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pressing the SHIFT and PRINT keys simultaneously. (In BASIC, SHIFT-PRINT points to the text "llist" followed by a carriage
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return in ROM... try it!) Both of these "buffers" are terminated by a null byte, or CHR$(0). The SHIFT-PRINT key can thus
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be useful in both BASIC and Machine Language programs.
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_____________________________________________________________________________________________________________________
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* "Carrier Detect in Basic"
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A useful routine has been uploaded to the SIG called DIALER.100 and was submitted by Jerry Kohl [71256,23]. It is heavily
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commented and explains a useful application of a routine that "times out" if carrier is not detected within a given amount
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of time. The routine also contains an npublished entry point to TERM mode within TELCOM without losing carrier.
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_____________________________________________________________________________________________________________________
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* Tandy BUG Department:
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The CHKDC ROM Call documented by Tandy at 5AA9H contains a "small" bug. It seems that the routine was actually written for
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the ADRSS and SCHEDL ROM programs to search for ADRS.DO and NOTE.DO. The limitation here is that the routine will only
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work if the filename being searched for contains 4 characters or less in the file name (preceding the required ".").
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How to get around this problem:
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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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_____________________________________________________________________________________________________________________
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* What is the Shack up to next?
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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
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repeated sometime at the end of March or beginning of April.
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_____________________________________________________________________________________________________________________
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* BREAK key disable
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Disabling the BREAK key can be accomplished by POKEing a value of 128 into the reserved RAM location 63056 (Hex F650).
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This effectively eliminates all of the top row of keys (function keys, etc.). To re-enable, just POKE the value 0 back
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into the same location.
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_____________________________________________________________________________________________________________________
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Model 100 ROM Calls
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This article is number two in the "hints and tricks" article for getting the most out of your Model 100. The topic of this
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particular session will be .
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Radio Shack has been kind enough to document quite a few ROM calls, but they do not state that these entry points are
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inviolate (ie. will not change with a new ROM revision), nor do they give too much information regarding how to use them
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in BASIC programs.
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The following is a series of ROM calls that can be used in to perform some odds and ends. To facilitate using some of the
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more "esoteric" calls, I will also be providing a method of providing an "interface" to BASIC variables.
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First, however, we will discuss the DOCUMENTED (by Tandy) ROM Calls that can be used directly in BASIC:
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DISC: 52BBH (21179 Decimal) Disconnect Phone Line
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This ROM Call will cause the internal modem to disconnect from the phone line.
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Typical BASIC Usage:
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CALL 21179
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_____________________________________________________________________________________________________________________
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CONN: 52D0H (21200) Pick up phone line
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This ROM Call will cause the internal modem to "pick up" the phone line. This would be used when trying to detect if
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carrier is present (see CARDET), but has other uses. A crude "dialing" mechanism could be done using the DISC and CONN ROM
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Calls to "pulse" the phone line. In fact, this is how the Model 100 actually dials!
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Typical BASIC usage:
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CALL 21200
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DIAL 532DH (21293) Dial phone number string @ (HL)
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Here we come to the first ROM call that requires a parameter.
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The call expects to find a valid phone number "string" (see manual on auto-dial strings) at the address pointed to by the
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HL register. It is not documented, but the phone number must have a "terminator". This can either be a NULL CHR$(0), or an
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"auto-log" string. If an auto-log string is used, the Model 100 will wait indefinitely for carrier before sending the
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auto-log string.
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Typical BASIC usage: (Autodialer)
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PH$="555-1212" + CHR$(0) :' Phone Number in
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PH$ V=VARPTR(PH$) :' Get addr of variable
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AD!=PEEK(V+1) + PEEK(V+2)*256 :' Get addr of string
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CALL 21293, 0, AD! :' Dial Phone Number
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CALL 21200 :' Keep Phone line open
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PRINT"Please pick up phone" :' Alert user
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INPUT"Enter when ready"; A$ :' Wait till picked up
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CALL 21179 :' Disconnect Model 100
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(Auto-logon -- terminal program)
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PH$="555-1212<=?U700000,0000^M?Ppsswrd^M?!G PCS154^M>" :' Phone Nbr + Auto Log
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V=VARPTR(PH$) :' Get addr of variable
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AD!=PEEK(V+1) + PEEK(V+2)*256 :' Get addr of string
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CALL 21293, 0, AD! :' Dial and auto log OPEN "MDM:7I1E" FOR INPUT AS 1 :' Open up Modem...
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OPEN "MDM:7I1E" FOR OUTPUT AS 2 :' for input and output ...
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_____________________________________________________________________________________________________________________
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CLRFLK 5A79H (23161) Clear function key definitions
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This ROM Call would be useful for resetting ALL the function key definitions. It is not too useful for BASIC programs, but
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it cannot be performed simillarly in a BASIC program (!).
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Typical BASIC usage:
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CALL 23161
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STFNK 5A7CH (23164) Set function key table
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CSFKEY 5B46H (23366) Cold Start Function key table address
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BASFKY F80AH (63498 or -2308) Current function key def's used by BASIC
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The STFNK call is often used in BASIC program to reset the function keys to their default cold start values. It can also
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be used to set the keys to any value desired. The STFNK call requires the address of a table of function key values to be
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stored at (HL), or the second argument to a CALL function.
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Typical BASIC program -- Reset to Cold Start values:
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CALL 23164, 0, 23366
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Typical BASIC program -- Change keys and reset back:
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A$="" :'Define a dummy string
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V=VARPTR(A$) :'Get addr of variable
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POKE V,128 :'128 characters long
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POKE V+1,10 :'Point to...
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POKE V+2,248 :'Current key def's
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B$=A$ :'Store def's in B$
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FOR X=16 TO 128 STEP 16 :'Set up delimiters
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C=ASC(MID$(B$,X,1)) OR 128 :'Get delimiter
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MID$(B$,X,1)=CHR$(C) :'Put it into string
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NEXT X :'Continue
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KEY 1, "F1" :'Now reset keys ... :'etc. at end of pgm:
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V=VARPTR(B$) :'Get addr of variable
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AD!=PEEK(V+1) + PEEK(V+2)*256 :'Get addr of key def's
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CALL 23164, 0, AD! :'Reset key definitions
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In the above example, the code up to the "KEY 1" statement is used to save the current function key settings into the
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variable B$. The STFNK function call requires that the definitions for all the keys be "delimited" by setting the most
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significant bit of the last byte. The FOR...NEXT loop performs this delimiting. At the end of the program, assuming that
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the variable B$ has not been modified, the last three instructions are performed, which reset the function key definitions
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to their original values.
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RCVX 6D6DH (28013) Return number of characters in RS-232 queue in A
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This ROM call is not too useful to be used directly in BASIC because BASIC has no way of returning values from ROM Calls.
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But... we can create a machine language "front end" that will suffice nicely. You do not need to know machine language to
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use this routine:
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00
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NOP ;Offset byte for call
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CD 6D 6D
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CALL RCVX ;Call routine 77
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LD (HL),A ;Store value in variable 23
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INC HL ;Bump pointer 36 00
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LD (HL),00H ;Zero MSB C9
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RET ;And return 00
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NOP ;Offset bytes
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The values on the left side of the listing above are the hexidecimal values of the assembly language instructions on the
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right. These values can be "paired" off to be stored in an "integer array" as shown below. The decimal equivalent of the
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integer pairs is shown to the right:
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00 CD -13056
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ML%(0) 6D 6D 28013
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ML%(1) 66 23 9062
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ML%(2) 36 00 54
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ML%(3) C9 00 201
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ML%(4)
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Thus, if we set up this array at the start of the program:
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DIM ML%(4) :' Reserve space
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FOR X=0 TO 4 :' Four values
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READ ML%(X) :' Store integer value
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NEXT X :' Continue
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DATA-31056,28013,9062,54,201 :' Data values
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At this point, we now have a relocatable machine language routine of our own. What does it do?? It allows us to call a ROM
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routine that returns a value in the A register, and get the value into an INTEGER variable in BASIC.
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How? Let's say that we want to call this routine stored in ML%(0-4) and return the value in the BASIC variable CT%.
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This would be accomplished as follows:
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CT%=0 :' Define variable
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CALL VARPTR(ML%(0)), 0, VARPTR(CT%) :' Do routine
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PRINT CT% :' Print the count
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Pretty simple, once it is implemented. The ML% array above is useful for other routines. All that need be changed is the
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value in ML%(1), which should contain the address of the routine to be called.
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_____________________________________________________________________________________________________________________
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RV232C (6D7EH) (28030) Get character from RS-232 to A register
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This routine is another that can be useful in BASIC in conjunction with the ML% array shown above. Change the value of
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ML%(1) to 28030 by executing a statement like:
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ML%(1) = 28030
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And the ML% routine can be used to get a character from the RS-232 queue. The advantage of using this routine (as opposed
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to the BASIC INPUT$ statement), is that ALL values passed from the RS-232 queue will be available. The INPUT$ statement
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does not allow the value CHR$(127) or CHR$(26)... in fact, receiving CHR$(26) has the effect of CLOSING the RS-232 file!!
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Typical BASIC program usage:
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REM ML% Array set up with ML%(1) = 28030
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CT% = 0 :' Initialize variable
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CALL VARPTR(ML%(0)), 0, VARPTR(CT%) :' Do routine
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PRINT CT% :' Print the char
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SENDCQ 6E0BH (28171) Send XON Resume character
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SENDCS 6E1EH (28190) Send XOFF Pause character
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These two routines are usefull for pausing and resuming transmission from a host that acknowleges XON/XOFF protocol.
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This can be useful for times when general "housekeeping" must be done. After an XOFF character (Pause) is sent, the host
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should stop transmitting. At that point, the program can do what it needs to do, such as outputing to a slow device (such
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as cassette), etc. When ready to resume transmission, send the XON character (Resume).
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Typical BASIC usage:
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CALL 28190 :'Send XOFF Pause
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GOSUB --- :'Do interesting things
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CALL 28171 :'Send XON Resume ... :'Continue receiving
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_____________________________________________________________________________________________________________________
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SD232C 6E23H (28195) Send character in A to RS-232 port
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This routine can be used to send a single character to the RS-232 port. In all actuality, there is no real benefit to
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using this call, as the PRINT # command allows you to send as many characters at a time as you wish with no restrictions.
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Typical BASIC program usage:
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CALL 28195, 3 :'Send ^C to HOST
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_____________________________________________________________________________________________________________________
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CARDET 6EEFH (28399) Return carrier detect status in A
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Since this routine returns a value, it is necessary to use a machine language "front end". The ML% array described above
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can be used if the statement:
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ML%(1) = 28399
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is executed. When the ML% routine is used to call the CARDET routine, the status returned is:
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0 Carrier Detected
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255 Carrier not found
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Typical BASIC program usage:
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REM ML% Array setup as described above
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CD% = 0 :'Initialize variable
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CALL VARPTR(ML%(0)), 0, VARPTR(CD%) :'Get carrier status
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IF CD% = 0 THEN PRINT"CARRIER DETECTED" ELSE PRINT"NO CARRIER"
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_____________________________________________________________________________________________________________________
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Look for other exciting installments in the near future.
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Comments and/or suggestions are welcome. Send them to larry gensch [72236,3516]
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