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6800 ROM MONITOR
VERSON 1.0
USERS GUIDE
Southwest Technical Products Corporation
219 W. Rhapsody San Antonio, Texas 78116
Copyright 1977, Southwest Technical Products Corporation
Scanned and edited by Michael Holley Sept. 17, 2000 Revised Aug. 6, 2002
Southwest Technical Products Corporation Document Circa 1977
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SWTPC SWTBUG® (SWATBUG) MONITOR ROM One of the features of the SWTPC 6800 Computer System is that the conventional programmer’s console has been replaced with a monitor ROM. The programmer’s console consists of all the pretty switches and lights often found on similar microcomputers that are used to bootstrap the system after power up. The programmer’s console not only raises the cost of the system, but more often than not is confusing and tedious to use for both be-ginning and experie
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SWTBUG® INSTALLATION SWTBUG® is a MOS device and MOS integrated circuits are susceptible to damage by static electricity. Although some degree of protection is provided internally within the integrated circuits, their cost demands the utmost in care. Before opening and/or installing SWTBUG® you should ground your body and all metallic tools coming into contact with the leads, thru a 1M ohm ¼ watt resistor. The ground must be an “earth” ground such as a water pipe, and not the circuit board
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MEMORY EXAMINE AND CHANGE M (addr) The Memory Examine and Change function can be used to enter machine code programs and to display and/or change the contents of memory. The Memory Examine and Change function should be used as follows: 1.) Type M. The computer should echo the M and output a space. 2.) Type in the four digit hexadecimal address that you wish to examine and/or change. The computer should respond with a carriage return, line feed, $, the address and the data that is stor
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The condition codes are as defined below: BIT NO. LABEL CONDITION CODE 0 C Carry-borrow 1 V Overflow 2 Z Zero 3 N Negative 4 I Interrupt mask 5 H Half carry In the above example the condition code of "3C" can be interpreted as follows: 3C = 0 0 1 1 1 1 0 0 16 BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 Below are two examples of how the R command works. Assume that this small program was entered to change certain registers. $M 0100 $0100 CE 8E LOADS STACK POINTE
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$R $FF DC FC 6EFD 0100 A042 REGISTER DUMP BEFORE RUNNING PROGRAM $G $R $FF DC FC 6EFD 0100 A042 NOTE R DUMP THE SAME AFTER RUNNING $J 0100 $R $FF DC FC 6EFD 0100 A042 THE SAME AFTER A JUMP $M 010A AT THIS POINT THE JUMP TO SWTBUG CONTROL $010A 7E 3F IS REPLACED BY A SWI. NOTE THE VALUE $010B 50 OF THE REGISTERS AFTER THE NEXT DUMP. $G $F9 FF 00 1234 010A 0FF9 REGISTER DUMP GIVEN BY SWI $R $F9 FF 00 1234 010A 0FF9 DUMP SHOWS PROGRAM CHANGES $ $FF DC FC 6EFD 0100 A042 R
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A002 à 01 MOST SIGNIFICANT BYTE OF LOWER ADDRESS A003 à 23 LEAST SIGNIFICANT BYTE OF LOWER ADDRESS A004 à 45 MOST SIGNIFICANT BYTE OF UPPER ADDRESS A005 à 67 LEAST SIGNIFICANT BYTE OF LOWER ADDRESS Typing P would turn the punch on and output the specified memory data. A sample punch output is as follows: $M A002 $A002 02 01 MSB OF LOW ADDRESS $A003 72 00 LSB OF LOW ADDRESS $A004 EF 01 MSB OF HIGH ADDRESS $A005 00 20 LSB OF HIGH ADDRESS $A006 5F $P TAPE PUNCH COMMAND S1130
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$M A048 $A048 01 00 $A049 03 05 $A04A F4 $P $S11300000A0501001EF023FF01A01B351B37022443 $E S105A04800050DS9 $ $ A048 and A049 are automatically transferred to A002-A005 and punched to tape by the E command. A short delay follows the S9 to allow clean load-ins on cassette tape. Appropriate punch on/off commands are automatically sent. TAPE LOADER FUNCTION L The L function is used to load either a MIKBUG® or SWTBUG® formatted program from either paper or cassette tape. To use
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A previously set breakpoint will remain and may be changed or removed as described earlier. If, when using the B command, a non-hex value is entered the previous breakpoint will be removed and SWTBUG® control will resume. There are several things that one must be aware of when using breakpoints to insure proper operation. 1.) The breakpoint function uses the same locations as do vectored software interrupts; therefore, vectored software interrupts should not be used with break points.
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VECTORED SOFTWARE INTERRUPTS Normally when encountering a SWI (3F) instruction, the computer will display the processor’s registers and SWTBUG® control will be resumed. If desired, the 3F command can be vectored to anywhere in memory, just like the NMI and IRQ interrupts. To use the vectoring capability simply store the service routine address at location A012-A013 in the SWTBUG® RAM. When a 3F is encountered, processor control will be transferred to the memory address stored in A012-A013.
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PIA STROBING Use of the Control Interface for Read/Punch-On/Off Decoding SWTBUG® software contains subroutines to send out pulses to unused pins of the PIA integrated circuit on the MP-C serial control interface that can be used for automatic reader / punch controls. These pulses can be used if you are using a SWTPC AC-30 cassette interface and a terminal in which access to the control command decoding is denied. If you intend to use the read/punch control logic output on the MP-C contr
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OPERATING THE MP-A PROCESSOR BOARD AT BAUD RATES HIGHER THAN 1200 BAUD When using the MP-S serial interface with an MP-A processor board, baud rate clocks for up to 9600 baud are available from the baud rate generator on the MP-A processor board. The table below shows the baud rates available and from which pin of IC4 on the MP-A board they are derived. These 16X baud rate clocks are best feed back to the interface boards via the user defined lines provided on the mother board. These baud
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NOTE: This does not mean that SWTBUG® is equipped with a binary loader-only certain SWTPC binary tapes that contain a special binary loader (in ASCII) will work correctly. To load the tape simply follow the instructions given for loading an ASCII tape, but keep the reader locked on. SPECIAL NOTES ON USING AN ACIA AND PROGRAM MODIFICATIONS Many available 6800 programs written for MIKBUG® assume that a PIA type MP-C control interface is being used and may address this port directly. When
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GENERAL RULES FOR PROGRAM WRITING Although for a user program to be functional it need only work with the exact system it was written for, following a few simple rules reduces program modifications for 6800 systems using other monitors. Following these rules will make your programs more professional and versatile. Some general guidelines are as follows: 1.) Minimize the number of references made to the ROM. 2.) Do not use strange, in-between SWTBUG® addresses. Generally only the routines
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SP (A008) Temporary storage location for the stack pointer. SP is used in the register dump subroutines and by the breakpoint function. PORADD (A00A) This location contains the port address used for SWTBUG’s I/O routines. PORECH (A00C) This byte tells SWTBUG® ‘s input routines whether or not to echo. XHI (A00D) Temporary index register storage used by numerous routines. XLOW (A00E) Temporary index register storage used by numerous routines. XTEMP (A010) Temporary index register stora
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INHEX and INCH, temporary storage locations CKSM and both accumulators. If a non-hex value is entered, SWTBUG® control will resume. When BYTE is called as a subroutine, the computer will wait for two hex characters to be entered thru the control port. If a 3C is entered, the results will be as follows: ACC A 3C ACC B CKSM IXR UNCHANGED CKSM Prior CKSM + check sum generated inside BYTE OUTHL (E067) These subroutines are used by OUT2HS and OUT4HS to output OUTHR (E06B) hexadecimal num
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ORG $100 START LDX #TEXT JSR PDATA1 JMP CONTRL TEXT FCB $0D, $0A FCC /HELLO/ FCB 4 END - The accumulator and register status after using PDATA1 is as follows: ACC A Changed during the operation ACC B UNCHANGED IXR Contains the memory location of the 04 CHANGE (E088) CHANGE is SWTBUG‘s memory examine and change function. Change uses a number of other SWTBUG® subroutines. OUT4HS (E0C8) OUT4HS is used to output a four-digit (16-bit) hexadecimal number onto the control termina
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CONTRL (E0E3) This MIKBUG® equivalent sequence again resets the stack to A042. PORECH is cleared to enable echo and the subroutine SAVGET is selected to get the correct port number and type. Next, the routines PNCHOF and RDOFF generate punch and reader off commands. A carriage return, line feed, erase to end of line (15 ) and a $ is then output to the control terminal. 16 At this point SWTBUG® is ready for command input. SFEl (E124) SFEl is the entry point for non user-vectored software i
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IOUT (E240) IOUT is the PIA output routine which outputs the character in the A accumulator. OPTL (E269) OPTL is the service routine that sets up PORECH for I/O on port 0. The appropriate command P, E or L is then selected. PIAECH (E27D) This routine disables the echo on a PIA type interface. PIAINI (E284) This routine is used to initialize PIA type interfaces. DELAY (E202) DELAY is a general purpose delay loop. If desired, the index register can be pre-loaded with a number other tha
