By andysa on the emulation forum on 6502.org

Here is the archive with source, documentation and the binary .uf2 file ready to run on a Pico,

It is based on Jonathans Fouvers “pico-6502 emulator” and “Fake6502”.
You will need this archive to compile the source of PicoSYM.

picoSYM Memory Map

• 32K RAM (0000 – 7FFF)
• Supermon V1.1 (8000 – 87FF)
• 1541DOS (9000 – 9FFF)
• VIA (A000 Block)
• System Ram (A600 – A67F)
• RAE assembler (B000 – BFFF / E000 – EFFF)
• Basic (C000 – DFFF)
• Basic Trig functions (F5C0 – F6EE)

PicoSYM emulates a SYM-1 with the Supermon V1.1 Monitor, Basic, RAE Assembler & Editor and 1541DOS at the typical addresses. The 1541DOS implementation uses “Port A” of an emulated VIA to connect to SD2IEC style floppy disk emulator modules. It has been tested with reasonable success with both the UIEC-SD and pi1541.

These SD2IEC type modules need to be connected to the RPi Pico GPIO ports via a suitable 3.3v/5v level converter and 7416 open collector inverter. (Refer SYM-1 1541 DOS manual and connection diagram within the ZIP file or the 1541 DOS page here)

The 1541DOS relies heavily on the VIA Timers, which required much experimentation with the emulator code in order to get operational. As such, the reliability has not been fully confirmed, however Loading, Saving of files and directory listings does appear to be functional and repeatable at this stage.

The only noticeable bug is with the Directory Listing reporting of “Blocks Free”, which contains erroneous characters. This is due to the 1541DOS simplistic decoding of the received IEC filesize data. This worked fine back in the day given the 170KB storage capacity of a floppy disk.

With the larger capacity of modern SD cards however, the reported free block size is larger than what the 1541DOS routines can accommodate. Partitioning SD cards to a smaller capacity should get around this problem in the short term, however andysa is in the process of patching the necessary subroutines in 1541DOS.

Usage
——-
To use the emulator, put the Raspberry Pi Pico in bootloader mode, by holding the ‘BootSel’ button while connecting it to a computer.
The Pico will appear as a drive. Drop the UF2 file to it.
Open a comms utility such as Putty, at 115200 baud (or use 2400 for a real SYM-1 experience!).

By andysa on the emulation forum on 6502.org

Here is the archive with source, documentation and the binary .uf2 file ready to run on a Pico,

It is based on Jonathans Fouvers “pico-6502 emulator” and “Fake6502”.
You will need this archive to compile the source of PicoSYM.

picoSYM Memory Map

• 32K RAM (0000 – 7FFF)
• Supermon V1.1 (8000 – 87FF)
• 1541DOS (9000 – 9FFF)
• VIA (A000 Block)
• System Ram (A600 – A67F)
• RAE assembler (B000 – BFFF / E000 – EFFF)
• Basic (C000 – DFFF)
• Basic Trig functions (F5C0 – F6EE)

PicoSYM emulates a SYM-1 with the Supermon V1.1 Monitor, Basic, RAE Assembler & Editor and 1541DOS at the typical addresses. The 1541DOS implementation uses “Port A” of an emulated VIA to connect to SD2IEC style floppy disk emulator modules. It has been tested with reasonable success with both the UIEC-SD and pi1541.

These SD2IEC type modules need to be connected to the RPi Pico GPIO ports via a suitable 3.3v/5v level converter and 7416 open collector inverter. (Refer SYM-1 1541 DOS manual and connection diagram within the ZIP file or the 1541 DOS page here)

The 1541DOS relies heavily on the VIA Timers, which required much experimentation with the emulator code in order to get operational. As such, the reliability has not been fully confirmed, however Loading, Saving of files and directory listings does appear to be functional and repeatable at this stage.

The only noticeable bug is with the Directory Listing reporting of “Blocks Free”, which contains erroneous characters. This is due to the 1541DOS simplistic decoding of the received IEC filesize data. This worked fine back in the day given the 170KB storage capacity of a floppy disk.

With the larger capacity of modern SD cards however, the reported free block size is larger than what the 1541DOS routines can accommodate. Partitioning SD cards to a smaller capacity should get around this problem in the short term, however andysa is in the process of patching the necessary subroutines in 1541DOS.

Usage
——-
To use the emulator, put the Raspberry Pi Pico in bootloader mode, by holding the ‘BootSel’ button while connecting it to a computer.
The Pico will appear as a drive. Drop the UF2 file to it.
Open a comms utility such as Putty, at 115200 baud (or use 2400 for a real SYM-1 experience!).

MICRO The 6502 Journal

Published by Robert M. Tripp, The Computerist
Published from 1977 tot 1983. The first years many KIM-1/SYM-1/AIM-65 articles, slowly faded to Apple Atari etc in later years, and ended in 1984.
The whole archive is here.

Best of MICRO 1

Best of MICRO 1, 1978

Best of MICRO 2

Best of MICRO 2 1979

Best of MICRO 3

Best of MICRO 3, AIM 65 SYM-1 KIM-1 part June 1979 May 1980

          KIM-1 / 6502 USER NOTES INDEX BY SUBJECT VOLUME 1(Issues 1 till 6)

APPLICATIONS FOR KIM             GENERAL INFORMATION
Application suggestions   1        Correction To Memory Map -------- 2
Calculator--Interface     4        Defective 6502 chips------------- 3
            Interface     6        Discussion of Memory Allocation - 5
          --T.I.5050      5        DISPLAY (on board)
Chess Clock Program       4           red filter for-----------------5
CONTROLLING                      Use of------------------------------1,5
 --- Function Generator   1        EXPANSION OF SYSTEM
 --- Light Intensity      4           KIMSI--------------------------4
 --- Motor Speed          4           MEMORY
 --- Touch tone encoder   1            Adding memory to KIM-1--------5
Degree Dispatch Computer  5            Diagnostic------------------- 2,5
Frequency Counter         3            Expansion---------------------4,3
                                  OSI Memory-------------------------3
GAMES                             Using SD Sales 4K RAM Board        3
  Bagels----------------- 5       Hardware tips
  Battleship--------------6          Packaging KIM-1 --------------- 6,3
  Horserace-------------- 3          Power Supply for KIM ---------- 4
  Hunt the Wampus-------- 2          Red Filter for Display----------5
  Jotto------------------ 5       INTERVAL TIMERS :
  Kimmaze---------------- 4          The Other Timer-----------------2
  Microchess------------- 3          and cassette                    2
  Mastermind------------- 5          Use Of--------------------------5,5
  Moon Lander-----------1,3       MIKIM------------------------------5
HEDEX Program             1       OPERATION TIPS
MATH TEST Program         4          Using SST  ---------------------2
Mini-l Loran-c            6          Using ST   to start programs----4
MUSIC:KlugeHarp     3,2,6,6       Page 1 Programming Problems--------6
Real Time Clock        4, 5       Packaging your KIM-1---------------3
Square wave generator     5       Power Supply-----------------------4
Stopwatch Program         2       Presetting 00F1, 00F2              4
Telephone Dialer        4,4         System Architecture              3
                                  Packaging your KIM-1---------------3
CASSETTE PROBLEMS/SUGGESTIONS     Presetting 00F1, 00F2              4
Certification of tape     6       System Architecture                3
Copying Cassette tape     3       TABLES for KIM-1
Fast tape problems        6          Interval Timer Table------------3
Hypertape               2,6           Relative Branch table----------2
Interval timer/cassette   1          OP Code table-------------------4
Notes on cassette         6       Techniques
PLL set program           5          Mnemonic Improvement------------41
PROBLEMS with Cassette    3                   BIT Data---------------41
Software control of tape         Top Down Programming                4
  reading                 4      Modifications/ IMPROVEMENTS
Speed up                  4         Crystal Stabilization------------5
Supertape                 2         Factory Mods. -------------------4
Supertape improvement     4         6502 Register Monitor Apparatus  4
Tape Certifying           6         74Ls145 ------------------------ 3,4
Tape Dupe                 4      6502 Microprocessor Board-----------6
Using Cassette            6         POWER ON RESET CIRCUIT           3
Varification of Data      4         NOTES FROM THE FACTORY           5
Vutape                    2      

                         INDEX Issue 13
                                                                     
SOFTWARE FEATURE                                                         1
     KIM Hexpawn (your KIM can learn to win)        Robert C. Leedon

6502 OP CODES (arranged logically for easy look up) Jim Butterfield      6

CASSETTE INTERFACE STUFF                                                 7
     Tape Verify II                                 Dr. Barry Tepperman
     Radio Tape Feedback                            Daniel Gardner
     Reliability Hint                               John Watney
     Help Relay Package Fixit                       Mike Firth
     Tape File Recovery Routine                     Loel Swank
     KIM Software On Cassette

LANGUAGE LAB                                                             10
     Focal
          I/O Mods                                  Editor
          Functions                                 Editor

     Basic
          I/O Mods                                  Marvin De Jong
          A Basic Question                          Editor
          Basic Timing Comments                     F. E. Kempisty
          KIM Basic Hint                            Micro-Z Company
          Basic Renumber Program                    Harvey Herman

     Tiny Basic
          Two Tiny Basic Mods                       Michael Day
          Ramblings About T.B.                      Lew Edwards

     Forth
          Forth Comments Example                   John P. Oliver

     Assemblers
          Two Pass Patch To Aresco Assembler        John Eaton
          Mods To MSS Assembler                     Richard M. Bender

DESIGN CORNER                                                           16
     A 6522 I/O Board

KIM-4 BUS PINOUT                                                         18

VIDEO  GRAPHICS                                                          19
     Video Displays                                 Editor
     Comments On Visible Memory                     Lew Edwards
     TVT-6 Adventure                                Dennis Chaput
     TVT-6 RAM Expansion                            Michael Allen
     Polymorphics Video Board Mods                  Editor

DEBUG                                                                    21
     Slow Stepper IV                                Lew Edwards

LETTERS  COMMENTS                                                        22

SOFTWARE LIBRARY
     Multi-Mode Adder                               Jim Butterfield
     Pseudo-Random Number Generator                 H. T. Gordon
     ASCII Dump Program                             Jim Zuber
     Keyboard Debounce Routine                      Thomas J. Rubens
     Sound Effects Program                          Bob Carlson
     Melodies For The Music Box                     Douglas Lyon
     'Do Loops'; For KIM                            Dave Skillman

INTERFACE                                                                26
     Camera Speed Tester                            Mike Firth
     Low-Cost Modem Possibility                     Editor
     RPN Calculator Chip Interface                  Editor
     Power-On Reset                                 George Hawkins
     The Outside World Connection                   Editor
     More On The Opto-Isolator                      Dwight Egbert

NEW PRODUCTS                                                             28
     Video Driver Package
     Price Decrease On Jolt Boards
     A 8080 Simulator For The 6502
     Eprom Programmer



                         INDEX Issue 14

INDEX
EDITORIAL
SOFTWARE FEATURES                                                         1
     KIM BANNER PROGRAM                             JIM ZUBER
     6KIM DISASSEMBLER
     CHECK-OUT                                      ROBERT LARRABEE


LANGUAGE LAB                                                             12
     BASIC
          MOD AND PROGRAMMING HINT                  HEINZ JOACHIM SCHILLING
          OUTPUT PAGING MOD                         DICK GRABOWSKY
          RENUMBER ADDENDUM AND SOME MODS           HARVEY HERMAN
          AUTOMATIC LINE NUMBER ENTRY MOD           SEAN MCKENNA
          A NEW COMMAND                             DICK GRABOWSKY
          PRODUCT ANNOUNCEMENT
          'USR' FUNCTION INFO                       C. KINGSTON
     FOCAL
     TINY BASIC
     FORTH
     XPL0


SYM SECTION                                                              18
     ACCESSING THE SYM DISPLAYS                     A.M. MACKAY
     SYM NOTES & KIM-4 COMPATIBILITY                C. KINGSTON
     WUMPUS   MUSIC BOX MODS                        JIM ADAMS


AIM SECTION                                                              19
     MANUAL CORRECTIONS                             JODY NELIS


VIDEO   TVT-6                                                            23
     POLYMORPHICS VIDEO/KIM INTERFACE               MIKE FIRTH
     TVT-6 NOTES & RAM EXPANSION                    MILAN MERHAR
     INTERFACING TO THE TVT II                      JOHN M. RENSBERGER

CASSETTE STUFF                                                           25
     MAKE A SHORT CASSETTE                          TED BEACH
     CASSETTE DIRECTORY PRINTOUT PROGRAM            CHRIS MCCORMACK

ANNOUNCEMENTS  REVIEWS

	KIM-1 User Notes Volume 0, July 1976
	KIM-1/6502 User Notes Volume 1, September 1976 KIM-1/6502 User Notes Volume 1, other version
	KIM-1/6502 User Notes Volume 2, November 1976 KIM-1/6502 User Notes Volume 2, other version
	KIM-1/6502 User Notes Volume 3, Januari 1977 KIM-1/6502 User Notes Volume 3, other version
	KIM-1/6502 User Notes Volume 4, March 1977 KIM-1/6502 User Notes Volume 4, other version
	KIM-1/6502 User Notes Volume 5 May 1977 KIM-1/6502 User Notes Volume 5 May 1977
	KIM-1/6502 User Notes Volume 6, July 1977 KIM-1/6502 User Notes Volume 6, other version
	KIM-1/6502 User Notes Volume 7/8, September November 1977 KIM-1/6502 User Notes Volume 7/8, Other version
	KIM-1/6502 User Notes Volume 9/10 January March 1978 KIM-1/6502 User Notes Volume 9/10 other version
	KIM-1/6502 User Notes Volume 11 May 78 KIM-1/6502 User Notes Volume 11 other version
	KIM-1/6502 User Notes Volume 12 KIM-1/6502 User Notes Volume 12 other version
	6502 User Notes Volume 13 6502 User Notes Volume 13. incomplete other version
	6502 User Notes Volume 14
	6502 User Notes Volume 15
	6502 User Notes Volume 16
	6502 User Notes Volume 17

Compute!

A magazine devoted mostly to 6502 computers.
Apart from the Compute II period,
before and afterwards also the small SBCs like
KIM-1, AIM 65 and SYM1 got attention of Compute!
High quality scans of Compute first years
with the SBC section, issue 1, 2, 3 and 7 to 19 , alas with a watermark.
Nearly all of Compute! lives here in html format.
The Internet archive has many issues without a watermark

Compute II

Compute II was a short lived split-off of Compute! and also a continuation of the KIM-1/6502 User Notes. Three issues and it was merged back with Compute! again.

	HTML version of Issue 1 PDF of Compute II Issue 1
	HTML version of Issue 2 PDF of Compute II Issue 2
	HTML version of Issue 3 PDF of Compute II Issue 3

Selected articles on KIM-1, AIM 65 and SYM-1 and 6502 in general

Articles by Marvin L. de Jong

	Interfacing the AM9511 and various floating point subroutines Compute! 7, 9, 11, 13, 17
	Computer Communications Experiments Compute! 10
	Experimenting With The 6551 ACIA Compute! 10
	Improved Pulse Counting Software For The 6522 Compute! 1
	Machine Language Versus Basic Prime Number Generation Compute! Issue 2
	The book by Marvin L. de Jong Programming and Interfacing the 6502 with Experiments

Articles on 6502, KIM-1, AIM 65, SYM-1

	Expanding KIM style 6502 SBC 3 part article in Compute 1981 January to March on the MTU bus
	Dungeons And Dragons Dice Simulator For The KIM-1 See also the program running on a KIM-1.
	A KIM-1 file in Microsoft Basic
	A Terminal for KAOS (KIM AIM, OSI, SYM)
	A Vocal HEX Dump for the KIM-1
	AIM 65 Floating-Point Arithmetic From Machine Language
	Placcating a Rebellious KIM Without Sacrificing RAM
	SYM (AIM) Hi Speed Tape Revisited
	AIM 65 Tape Copy Utility
	AIM User Input And Output
	An Efficient AD Interface
	Cassette IO with AIM 65 BASiC
	BASIC Memory Map KIM AIM SYM PET APPL
	Combining BASIC And Machine Language Programs On Tape
	Communication
	Dissecting C.W. Moser’s ASSMTED 1.0
	DLOAD AIM Memory Loader
	Hex Conversion
	KIM Tidbits Expanding The System
	KIM-1 Tidbits BASIC input
	Load And Save KIM Basic Programs on Your SYM
	Nuts and Volts 6 Centronics via 6522
	Nuts And Volts 6502 Read and Write Timing
	Read PET Tapes With Your AIM
	Real Time Clock Subroutine
	SYMple Clock
	Test RAM for bad bits Nondestructivily
	The Practical Aspects of Assembly Language Programming Part 1 and 2
	The Practical Side of Assembly Language
	The Single-Board 6502 The KIM-4 Bus
	The Single-Board 6502 High Speed Data transfer
	The Wonderful Wedge
	Track Down Those Memory Bugs
	Using The 6522 to drive a Printer
	The Carry Bit What it is And How it works

Note that the KIM/MTU bus is still in use in the replica boards series designed by Eduardo Casino, see his repository here for buffered and an unbuffered version.

MTU K-1005 Card File and 5 slot Motherboard using KIM/MTU bus

All MTU expansions, be it card cages with motherboards, memory, video, floppy disk cards use the MTU/KIM-1 bus.

PRINCIPLES OF OPERATION
Actually there is not much theory behind the operation of 5 edge connectors, 44 parallel wires and a terminal strip. What can be discussed however is the philosophy behind the K-1005 series of card files and its associated KIM/MTU bus. The Commodore KIM-1 single-board microcomputer was first released in 1976 and is the grandparent of the Synertek SYM-1 (formerly the VIM-1) and Rockwell AIM-65 micro-computers. Even the Commodore PET shows some KIM-1 influence. These processors cover the vast majority of 6502 based systems in use today and are the ones supported most vigorously by MTU.

WHY THE KIM BUS?
The original KIM-1 was a well thought-out product that hit on just the right tradeoff between system resources and selling price. Some amazing things have been done in its 1K memory such as the first generally available microcomputer chess program, the first 4 voice all software music synthesis program, Tiny BASIC, and others. However at some point every system needs to be expanded and the KIM and its relatives are no exception.
Commodore’s answer for expansion was the KIM-4 expansion bus and KIM-3 memory board. Independent manufacturers introduced similar expansion bus boards while others offered expansion systems based on the Altair (S-100) bus. The S-100 bus adapters were more successful because there was a multitude of expansion boards from which to choose. One pitfall in the S-100 technique is that not all S-100 boards would work properly with 6502 timing signals. The main common fault with the mechanical implementation of these products is their open-air construction which offers little protection for the boards and eliminates portability.
MTU’s first KIM expansion product was the K-1008 Visible Memory. The idea behind the VM was to have a board at the price of a plain 8K memory which would also show a high resolution video image. The goal was to capture both the KIM add-on memory and video display market with a single product. In deciding how it should connect to the KIM we had several factors to consider. First, it seemed like a poor idea to produce a board to plug into a bus (KIM-4) that few potential customers had. On the other hand an S-100 environment would have prohibited our use of 6502 timing properties to produce a totally transparent memory and snow-free display. In the final analysis it seemed desirable to produce a board that re-quired no motherboard or bus at all to connect and thus be available at a much lower “installed” price. The logical conclusion was simply direct parallel connection to the KIM-1 Expansion connector!
The KIM BUS, which is the signals on the KIM’s expansion edge connector, for the most part uses the actual signals from the 6502 microcomputer itself. Further-more the SYM-1 and AIM-65 Expansion connector busses are for practical purposes identical to the KIM-1 bus. The combined number of these processors sold makes the KIM bus one of the most widely used and to date has suffered less from compatibility problems than any other multi-vendor personal computer bus structure.
We have since designed and manufactured 4 additional expansion boards that may be used alone in the same manner. In order to support those customers who wish to use several of our expansion boards, we designed the K-1005 motherboard/card file which is simply a convenient method of connecting several boards to the processor’s expansion connector along with the necessary mechanical support provisions.

PLAIN OR BUFFERED?
Probably the most frequently asked question regarding the K-1005 is “Why is the bus not buffered?”. The basic answer is that buffering is not needed for only 4 expansion boards. The next question then is “Why not buffer it anyway to reduce microprocessor loading, provide noise immunity, and improve signal rise times?”. The answer to that is somewhat more technical but in a nutshell buffering has some of its own problems and it is not necessarily true that it improves system operating margins when the unbuffered equivalent does not violate any loading rules.
The KIM bus address and data lines are simply the corresponding microprocessor busses brought out to edge fingers. The various control signals (PHASE 2 and READ/WRITE) are indeed buffered by TTL gates on the processor board. The unbuffered address and data lines are rated by the microprocessor manufacturer to drive 1.7MA of DC loading and 170pF of capacitance. This figures out to 5 low power Schottky TTL (74LS series) inputs (MOS inputs such as to memory IC’s have no DC load) and about 35 circuit connections at 5pF per connection. The processor board itself uses one low power Schottky load and about a dozen connections (more connections on SYM and AIM processors). This leaves 4 low power Schottky inputs and over a dozen connections for the external bus which is adequate for implementing a 4 slot expansion bus. This is the main reason the K-1005 has 5 slots including processor.
Probably the most misunderstood aspect of buffering is noise generation and immunity. In theory low impedance TTL or TRI-STATE bus drivers should be able to “short out” noise spikes much better than high impedance MOS outputs can. This may be true, but in practice TTL or high power TRI-STATE bus buffers generate so much noise when they switch that almost nothing can absorb it. The problem is most acute in large systems (such as minicomputers and S-100 computers) where as many as 24 buffers with 100MA surge capability and nanosecond rise times can switch simultaneously thus placing a 2.5 amp reaction current surge through the GROUND leads of the bus. It is not unusual to see over a half volt differential in GROUND voltages between driving and receiving boards in such a system. In practice such spikes interfere with the bus CONTROL signals which results in unpredictable occurrances such as spurious writing into memory or falsely triggering an I/O device. Seldom are address and data bus signals themselves read wrong even though they cause the noise because they are ignored while changing (under the direction of control signals). indicate that all changing must have ended and the data be stable at it’s “0” or “1” state. It is instructive to note that minicomputer busses (such as the DEC UNIBUS and the NOVA bus) specify the use of filter and delay circuits on control signal lines received by interface boards. In addition, these systems typically have multilayer backplanes with ground planes to shield and shunt noise.
With unbuffered MOS and low power (8 MA) 74LS TTL bus drivers, such noise is almost completely absent. The author has had considerable experience in designing and troubleshooting bus systems and the unbuffered KIM bus is among the quietest encountered. With respect to rise time, 8MA is sufficient to swing 170PF (which is actually a rather heavy bus load) from logic zero to one or vice-versa within 65NS which is quite adequate for 1MHz 6502 operation. Note that this time has already been factored into the 6502 timing specifications. Remember also that bus buffers do have their own propagation delay times.

KIM BUS -VS- KIM/MTU BUS
As the reader may have guessed, the bus implemented on the K—1005 motherboard is not strictly a KIM—I bus. If it were, all 44 lines would be run strictly parallel up and down the board. The MTU modification amounts to assigning the top slot to the CPU (except for the PET version where all slots are equivalent) and not connecting some of the pins to the expansion bus below. This then frees up several lines on the expansion bus for other functions that do not relate to the CPU or computer bus operation,
Two of the pins are used to provide unregulated +8 and +16 volt power to the expansion boards, which the CPU does not use, Two more pins are used for the DECODE ENABLE and VECTOR FETCH signals that KIM-I systems require (unnecessary for AIM—65 and SYM—1). An additional three pins are used (in PET systems only) to carry separated Vertical, Horizontal and Video signals to a separate sync video monitor. Finally there is one spare set aside for future use. The following page lists the signals of each processor and those of the KIM/MTU bus used on the K-1005.

In providing these expansion bus signals, some signals from the CPU are not available on the bus, The most significant of these are READY and PHASE 1, PHASE 1 is equivalent to PHASE 2 the inverse of PHASE 2 which is available on the bus, Modern memories are fast enough so that wait states are not needed, thus the •READY signal. is of no use, Besides, the 6502 will not wait during a write cycle anyway.

I have added some photos from a Seawell Little Mother Board and Seawall SRAM card on the Seawell page. KIM-1 SYM_1 and AIM 65 expansion boards.

Now with the manuals scanned by Clayton Seale, thanks!