Model 100 System Map Part 0

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Origin

This is a derived work of the "Model 100 System Map", Copyright (C) 1985, Robert D. Covington, Systems Information Management Consultants.

File Formats

 .BA Files:
           2 bytes -  Address of next line
           2 bytes -  Line number
           Up to 255 characters ending with a null
           EOF is 3 consecutive nulls

 .DO Files:
           Text ended with a EOF character 1AH

 .CO Files:
           2 bytes -  Address to load to
           2 bytes -  Number of bytes to load (-start 6)
           2 bytes -  Transfer address

File Descriptor Block Format

The File Descriptor Block is the address given by VARPTR(#file).

Byte:
      0 - File status (0-not open, 1-open for input, 2 open for 
          output or append)
  2 & 3 - Address of file directory entry
      4 - File device (248-RAM, 249-MoDeM, 250-LinePrinTer, 
          251-WAND, 252-COM, 253-CASsette, 254-CRT, 255-LCD)
      6 - Offset from buffer start (see bytes 9) for start of next 
          record
      7 & 8 -  Relative position of next 256 byte block from
          beginning of file
      9 - Start of 256 byte buffer for data transfer

Floating Point Accumulator Format

---------------------------------------------------------------
 FAC1   |  FAC2   |     DP    |    SP    |  Integer |   SP
Address | Address |   Format  |  Format  |  Format  | Register
---------------------------------------------------------------
FC18H   | FC69H   |   S & E   |  S & E   |    -     |    C
FC19H   | FC6AH   |   BCD M   |  BCD M   |    -     |    B
FC1AH   | FC6BH   |   BCD #   |  BCD #   |   LSB    |    E
FC1BH   | FC6CH   |   BCD #   |  BCD L   |   MSB    |    D
FC1CH   | FC6DH   |   BCD #   |    -     |    -     |    -
FC1DH   | FC6EH   |   BCD #   |    -     |    -     |    -
FC1EH   | FC6FH   |   BCD #   |    -     |    -     |    -
FC1FH   | FC70H   |   BCD L   |    -     |    -     |    -
---------------------------------------------------------------

  LSB =  Least significant byte of intger
  MSB =  Most significant byte of integer.  Bit 7 contains the sign 
        of the integer
BCD L =  Least significant BCD byte
BCD H =  Most significant BCD byte
BCD # =  Middle BCD bytes.  Each digit of the number is represented 
        by one of the values in the two nibbles in each byte
S & E =  Sign and exponent of each number.  Bit 7 contains the sign 
        of the floating point number. Bit 6 must be set.  Bits 0-5 
        determine where the decimal point is to be inserted.  For 
        example, if this byte contained a 65, the sign would be 
        positive and the decimal point would be placed between the 
        first and second digits (#.###....)

Option ROM Important Addresses


40H = 54H
41H = 43H - Required for ROM to be detected on BOOT
42H - 47H - Name of file associated with ROM program

Code at 7E24H-7E43H executed on BOOT to handle option ROM.
Code at 0365H loaded at F605H on BOOT to detect option ROM.

Model 100 Hardware Port Map

A0H -  Modem control port
      Output:
        Bit:
            0 - Modem telephone relay (1-Modem connected to phone 
                line)
            1 - Modem enable (1-Modem chip enabled)

B0H -  8155 PIO Command/Status Register
      Output:
        Bit:
            0 - Direction of Port A (0-input, 1-output)
            1 - Direction of Port B (0-input, 1-output)
        2 & 3 - Port C definition (00 - All input, 11 - All output, 
                01 - Alt 3, 10 - Alt 4 (see Intel technical sheets 
                for more information))
            4 - Enable Port A interrupt (1 - enable)
            5 - Enable Port B interrupt (1 - enable)
        6 & 7 - Timer mode (00 - No effect on counter, 01 - Stop 
                counter immediately, 10 - Stop counter after TC, 11 
                - Start counter)
      Input:
        Bit:
            0 - Port A interrupt request
            1 - Port A buffer full/empty (input/output)
            2 - Port A interrupt enabled
            3 - Port B interrupt request
            4 - Port B buffer full/empty (input/output)
            5 - Port B interrupt enabled
            6 - Timer interrupt (status of TC pin)
            7 - Not used

B1H -  8155 PIO Port A
      Output:
        8 bit data port for printer output, keyboard column strobe, 
        and LCD
        In addition, the first 5 bits of this port is used to 
        control the 1990 real time clock chip.  The configuration of 
        these five bits are:
        Bit:
            0 -  C0
            1 -  C1
            2 -  C2
            3 -  Clock
            4 -  Serial data into clock chip


B2H -  8155 PIO Port B.
      Output:
        Bit:
            0 - Column 9 select line for keyboard.  This line is 
                also used for the CS-28 line of the LCD.
            1 - CS 29 line of LCD
            2 - Beep toggle (1-Data from bit 5, 0-Data from 8155 
                timer)
            3 - Serial toggle (1-Modem, 0-RS232)
            4 - Software on/off switch for computer
            5 - Data to beeper if bit 2 set.  Set if bit 2 low.
            6 - DTR (not) line for RS232
            7 - RTS (not) line for RS232

B3H -  8155 PIO Port C
      Input:
        Bits:
            0 - Serial data input from clock chip
            1 - Busy (not) signal from printer
            2 - Busy signal from printer
            3 - Data from BCR
            4 - CTS (not) line from RS232
            5 - DSR (not) line from RS232
            6-7 - Not avaiable on 8155

B4H -  8155 Timer register.  LSB of timer counter

B5H -  8155 Timer register.  MSB of timer counter

B8H -  Same as port B0H

B9H - Same as port B1H

BAH - Same as port B2H

BBH - Same as port B3H

BCH - Same as port B4H

BDH - Same as port B5H

C0H -  Bidirectional data bus for UART (6402) (C0H-CFH same)


D0H -  Status control register for UART, modem, and phone (6402) 
      (D0H-DFH same)
      Output:
        Bits:
            0 - Stop Bits (1-1.5, 0-2)
            1 - Parity (1-even, 0-odd)
            2 - Parity Enable (1-no parity, 0-parity enabled)
            3 - Data length (00-5 bits, 10-6 bits, 01-7 bits, 11-8 
                bits)
            4 - Data length (see bit 3)
      Input:
        Bits:
            0 - Data on telephone line (used to detect carrier)
            1 - Overrun error from UART
            2 - Framing error from UART
            3 - Parity error from UART
            4 - Transmit buffer empty from UART
            5 - Ring line on modem connector
            6 - Not used
            7 - Low Power signal from power supply (LPS not)

E0H -  Keyboard input and misc. device select (E0H-EFH same)
      Output:
        Bits:
            0 - ROM select (0-Standard ROM, 1-Option ROM)
            1 - STROBE (not) signal to printer
            2 - STROBE for Clock chip (1990)
            3 - Remote plug control signal
      Input:
            8 bit data row from keyboard strobe

F0H - LCD display data bus (F0H-FFH same)

Model 100 Keyboard Matrix

           ------------------------------------------------
          7 |  L    K    I    ?    *    ->   Ent  f8   Brk
Row       6 |  M    J    U    >    &    <-   Prt  f7   
In        5 |  N    H    Y    <    ^    Up   Lbl  f6   Cap
          4 |  B    G    T    "    %    Dwn  Pst  f5   Num
0E0H-     3 |  V    F    R    :    $    +    Esc  f4   Cde
0EFH      2 |  C    D    E    ]    #    -    Tab  f3   Gph
(224-     1 |  X    S    W    P    @    )    Del  f2   Ctl
239)      0 |  Z    A    Q    O    !    (    Spc  f1   Sft
           ------------------------------------------------
         bit  0    1    2    3    4    5    6    7    0
             [----------- 0B1H or 0B9H -----------] [0B2H]
             [----------- 177  or 185 ------------] [178 ]
                           Column Strobe

Note:     This table is incorrectly documented in Radio Shack's 
         "Model 100 Technical Reference Manual" (26-3810)

Math Routine Summary

-------------------------------------------------------------
Function       Single Precision    Double Precision    Integer
-------------------------------------------------------------
    +               37F4H               2B78H           3704H
    -               37FDH               2B69H           36F8H
    *               3803H               2CFFH           3725H
    /               380EH               2DC7H           0F0DH
    ^               3D7FH               3D8EH           3DF7H
 Compare            3498H               34FAH           34C2H
-------------------------------------------------------------

RIM and SIM Bit Maps

SIM Bit 0: RST 5.5 mask (set mask) RIM Bit 0: RST 5.5 mask
        1: RST 6.5 mask (set mask)          1: RST 6.5 mask
        2: RST 7.5 mask (set mask)          2: RST 7.5 mask
        3: Mask set enable                  3: Int. enable
        4: Reset RST 7.5 flip/flop          4: RST 5.5 pending
        5: Not used                         5: RST 6.5 pending
        6: SOD change enable                6: RST 7.5 pending
        7: SOD pin output                   7: SOD pin input

Note: SOD pin is used for cassette I/O on Model 100

Model 100 Special Control Characters

--------------------------------------------------------------
Control Code |  Print  | Routine |                            
  Sequence   | Address | Address |        Description         
--------------------------------------------------------------
Beep (7)         4229H     7662H   Beep
Tab (9)            -       4480H   Tab cursor
LF (10)          4225H     4494H   Move down one line
Home (11)        422DH     44A8H   Home cursor
CLS (12)         4231H     4548H   Clear screen
CR (13)            -       44AAH   Move cursor to beginning of 
                                   next line
ESC A              -       4469H   Move cursor up one line
ESC B              -       446EH   Move cursor down one line
ESC C              -       4453H   Move cursor to the right
ESC D              -       445CH   Move cursor to the left
ESC E              -       4548H   Clear screen
ESC H              -       44A8H   Home cursor
ESC J              -       454EH   
ESC K            425DH     4537H   Erase from the cursor to the 
                                   end of the screen
ESC L            4258H     44EAH   Insert blank line at current 
                                   line
ESC M            4253H     44C4H   Delete current line
ESC P            4249H     44AFH   Turn cursor on
ESC Q            424EH     44BAH   Turn cursor off
ESC T            4235H     4439H   Protect line 8
ESC U            423AH     4437H   Unprotect line 8
ESC V            423FH     443FH   Stop automatic scrolling
ESC W            4244H     4440H   Resume automatic scrolling
ESC X            4262H     444AH   
ESC Y            427CH     43AFH   Set cursor position.  
                                   Coordinate for cursor (row 
                                   and column) follow ESC Y 
                                   sequence
ESC j              -       4548H   Clear screen
ESC l              -       4535H   Erase current line
ESC p              -       4431H   Start inverse video mode
ESC q              -       4432H   Cancel inverse video mode

History

This documented was created with well over 200 hours of sweating over a Model 100 ROM disassembly. I started my first research on the Model 100 ROM about 2 hours after purchasing it (Note: I had one of the first 100's off the production line. I believe I purchased my 100 in June of 1983). After I figured out how to use TELCOM, I downloaded a BASIC Z-80 disassembler that friend of mine (Mike Livorsi) wrote from my Model 3. After making a few changes to the disassembler, I was able to get it to work on the Model 100. Then, I tested my Model 100's parallel printer port by printing a disassembly of the Model 100's ROM on my old LP8 (note:the disassembly requires a 3 inch note book to fit in). A day later, I came back to my Model 100 and found what every machine language addict loves; a complete dissasembly of the ROM.

At this point, I had a big problem; where to start. At the time, the only documentation for the 100 was the Instruction Manual. "Hacker reliefs" like schematics, memory maps, debuggers, etc. could only be found in the dreams of the infant portable hackers.

What did I end up doing? Well, I decided to write a little BASIC program to search for specific bytes in ROM. This program was used initially for finding the text string "Ok" in ROM. Once I found out where the message was in ROM, I then searched for any ML instructions that referenced the message. Then, on a warm July night in St. Louis, I found what I was looking for; a 16 bit register load that referenced the message "Ok" followed by a CALL instruction. This was the key I needed to open the door to the Model 100's ROM. With my experience from the Model 1/3/Coco ROMs, I knew that the load/CALL sequence I found was used to print a text string on the screen. From this little information, I was able to interrogate the subroutine called and find out how the display operated. In addition, since "Ok" is only printed at BASIC ready, I was able to trace out the keyboard input routines and eventually, the entire BASIC interpreter.

About 200 or so hours later, I documented most of the Model 100's ROM. At this time, I knew enough about my Model 100 to write just about any machine langauge program that I needed.

When I started writing ML programs for the 100, I found one problem with my ROM documentation; it was too hard to find a particular ROM address. What I needed was an organized collection of all my notes, "chicken scratches", etc.

From this came the memory map you hold in your hand right now. In this memory map, I basically included the information that I use the most when ML programming. I did not include a lot of information on how the ROM handles certain task, but I did include information that can be used by external stand alone ML programs.

References

In creating this document, I had a little help along the way with figuring out a few things. Below is a list of sources I used to help me determine or verify what certain things in the Model 100 did:

  • Model 100 User Manual, Radio Shack
  • Model 100 Service Manual (26-3801), Radio Shack
  • Microsystem Components Handbook, Volume 1, Intel (1984)
  • MOS Microprocessors and Peripherals, Advanced Micro Devices (1983)
  • Microsoft BASIC Decoded & other Mysteries for the TRS-80, by James Lee Farvour, IJG (December 1982)
  • "Inside the 100", by David P. Sumner, 80 Micro (December 1983)