SIMPLE-68008

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SIMPLE-68008 P475-720px.jpg

Features

  • 68008 CPU
    • 20 bit address space (1MB total)
  • 10 MHz clock
  • 128KB/512KB SRAM
    • Runs with zero wait states
  • Up to 448KB EPROM/EEPROM
    • Runs with zero wait states
  • 68681 Dual Serial Port (ACIA)
    • Headers for FTDI
    • 38,400 baud (other rates are programmable)
    • Connected to FTDI-49MM card
      • FTDI-49MM card drives 5V to the card
      • Run serial terminal program on the PC
  • Reset switch with optional Power Supervisor
  • 5V operation
    • 375 mA nominal
  • 95x95mm card
  • (4) 6-32 mounting holes

Memory Map

  • 0x00000-0x7FFFF 512KB SRAM
  • 0x80000-0xEFFFF Up to 448KB EPROM (minus DUART I/O space)
  • 0x80000 write with D0 = 1 to unmap the EPROM from the SRAM space
  • 0x80000-0x87FFF 27C256 (322KB)
  • 0x80000-0x8FFFF 27C512 (64KB)
  • 0xF0000-0xFFFFF Serial (ACIA)

Alternate Memory Map

  • Other memory maps could be done
  • For instance, the Teeside memory map could be used
  • The memory map depends on two things
    • Mapping in the PLDs
    • The firmware that is being run on the card has to match the memory map

Chip Set

  • On Ebay
    • $20 plus $9 shipping (2024-08)

EBAY 68000 SET.jpg

Parts in "Kit"

  • Only the MC68000P10 and TMP68681P are used by this card
  • MC68000P10 - 68K CPU with 16-bit data bus and 24-bit address bus
  • TMP68681P - Dual UART, 8-bit I/O, 6-bit I/O
  • MC68230P8 - Parallel I/O bits, timer
  • MC68901P - Multifunction (8 I/O pins, interrupt controller, (4) timers, UART
  • AM8511A - Floating Point Unit
  • MC68008P10 - 68K CPU with 8-bit data bus and 20-bit address bus
  • 65B50P - ACIA (Serial interface)

Design

CPU

  • The Motorola 68008 is an 8/32-bit microprocessor introduced by Motorola in 1982
    • It is a version of 1979's Motorola 68000 with an 8-bit external data bus, as well as a smaller address bus
    • This card uses a 68008 with 20 address lines (48-pin package) which allowed 1 MB address space versus the 16 MB addressable on the 68000
  • Rev 1 needs a wire jumper U5-39 to U5-40 to pull up VPA*

SIMPLE-68008 U5 CPU.PNG

CPU Timing

CPU Timing-A01.PNG

CPU Timing-B01.PNG

Function Code

CPU Function Codes.PNG

EPROM

SIMPLE-68008 U8 EPROM.PNG

  • SST27C256 EEPROM
    • 32 KB part
    • 28 pin part, 32 pin socket
  • SST27C512 EEPROM
    • 64 KB part
    • 28 pin part, 32 pin socket

Flash Memory (EEPROM) Programming

  • Program using TL-866ii plus programmer
  • Select device type
  • File Open
  • Select file = S68K_001.hex
  • File format: INTEL_HEX
  • To Region: Default
  • Set EPROM offset when file is loaded to accommodate memory map offsets for EPROM space
    • Set From File Start Addr(Hex) to 80000
    • To Buffer Start Addr(Hex) to 00000 (should be already that value)

SIMPLE-68008 EEPROM Programmer-02.PNG

  • Got Device ID error
    • Turn off ID checkbox in the Options section (bottom left of window)
    • Using SST 27SF512 part (Part is 64 KB)
      • Parts are actually Winbond parts remarked as SST
      • Looking up device ID showed the parts are actually Winbond parts
      • Can set programmer to Winbond part and it programs without error
  • Device programmed/verified
  • Memory Buffer should look like

SIMPLE-68008 EEPROM Programmer.PNG

Device ID Mysteries

  • Ebay has parts with SST marking
  • EPROM Programmer says the parts are WinBond (Manufacturer ID 0xDA)
  • Part marked as 27SF512 and it's a 27C512 (Part ID 0x08)
  • Windbond 27C512 qty 10 are cheaper than SST part on ebay

SRAM

SIMPLE-68008 U7 SRAM.PNG

  • Using 512 KB SRAM
    • Wire jumper H6-2 to H6-3 on rear of card

Dual UART

SIMPLE-68008 U6 DUART.PNG

Reset

SIMPLE-68008 U4 RESET.PNG

Clock

SIMPLE-68008 U1 OSC.PNG

  • Test and works with 8 MHZ and 10 MHz crystal oscillator

PLDs

PLD Programming TL866.PNG

PLD_001

SIMPLE-68008 PLD 001.png

PLD_001 Source Listing
Name       SIMPLE-68008_PLD_1;
Partno     ATF16V8B;
Date       07/13/24;
Revision   01;
Designer   DOUG G;
Company    LAND BOARDS LLC;
Assembly   U02;
Location   RUSTBELT, USA;
Device     G16V8;

/*
*/

/* Inputs */
PIN    1   = CLK;
PIN    2   = !CPUAS;
PIN    3   = !CPUDS;
PIN    4   = CPUA16;
PIN    5   = CPUA17;
PIN    6   = CPUA18;
PIN    7   = CPUA19;
PIN    8   = CPUFC0;
PIN    9   = CPUFC1;
PIN    11  = CPUFC2;
PIN    12  = !DDTACK;
PIN    13  = SWAP;

/* Outputs */
PIN    14  = !CPUIACK;
PIN    15  = !DUARTCS;
PIN    16  = !CPUDTACK;
PIN    17  = WAIT1;
PIN    18  = !RAMSEL;
PIN    19  = WAIT2;

CPUIACK = CPUA19 & CPUA18 & CPUA17 & CPUA16 & CPUFC2 & CPUFC1 & CPUFC0 & CPUDS;

DUARTCS = CPUA19 & CPUA18 & CPUA17 & CPUA16 & CPUDS & !CPUFC1 &  CPUFC0;

RAMSEL = !CPUA19 & SWAP & CPUDS & !CPUFC1 &  CPUFC0  		/* User/Super Data */
#        !CPUA19 & SWAP & CPUDS &  CPUFC1 & !CPUFC0; 		/* User/Super Program */

CPUDTACK = CPUA19 & CPUA18 & CPUA17 & CPUA16 & CPUDS & !CPUFC1 & CPUFC0 & DDTACK		/* DUART Data spaces	*/
#	    CPUA19 & CPUA18 & CPUA17 & CPUA16 & CPUDS & CPUFC2 & CPUFC1 & CPUFC0 & DDTACK	/* DUART IACK space */
#          CPUA19 & !CPUA18 & CPUDS								/* EPROM	*/
#          CPUA19 & !CPUA17 & CPUDS								/* EPROM	*/
#          CPUA19 & !CPUA16 & CPUDS								/* EPROM	*/
#          !CPUA19 & CPUDS;									/* RAM 		*/

PLD_002

  • The SWAP line maps the EPROM to the SRAM space
    • EPROM map addresses still work and are mapped to 0x8000-0xEFFFF
    • Used to pull the Stack pointer and start address from EPROM
    • Set to 0 at power up
    • Write to address 0x80000 with D0 = 1 to unmap the EPROM from the SRAM space
    • Needs to be set early in the startup code before SRAM is accessed

SIMPLE-68008 PLD 002.png

PLD_002 Source Listing
Name       SIMPLE-68008_PLD_2;
Partno     ATF16V8B;
Date       06/19/24;
Revision   01;
Designer   DOUG G;
Company    LAND BOARDS LLC;
Assembly   U03;
Location   RUSTBELT, USA;
Device     G16V8;

/*
	RESET CONTROLLER, ROM CHIP SELECT
*/

/* Inputs */
PIN    1   = CLK;
PIN    2   = !CPUWR;
PIN    3   = !CPUDS;
PIN    4   = CPUA16;
PIN    5   = CPUA17;
PIN    6   = CPUA18;
PIN    7   = CPUA19;
PIN    8   = !POR;
PIN    9   = CPUD0;

/* Outputs */
PIN	  13  = SWAPADR;
PIN    14  = SWAP;
PIN    15  = !ROMCS;
PIN    16  = !MEMRD;
PIN    18  = !CPUHLT;
PIN    19  = !CPURES;

/* CLEAR SWAP AT POWER UP, RESET	*/
/* SET SWAP BY 1ST WR TO START OF EPROM SPACE		*/
/* SWAP.CK = CLK; */
/* SWAP.AR = POR; */

MEMRD = !CPUWR & CPUDS & !CPUA19
#       !CPUWR & CPUDS &  CPUA19 & !CPUA18
#       !CPUWR & CPUDS &  CPUA19 & !CPUA17
#       !CPUWR & CPUDS &  CPUA19 & !CPUA16;

SWAP = CPUDS &  CPUWR & CPUA19 & !CPUA18 & !CPUA17 & !CPUA16 & CPUD0 & !POR
#      SWAP  & !POR;

SWAPADR = CPUDS & CPUWR & CPUA19 & !CPUA18 & !CPUA17 & !CPUA16;

ROMCS = CPUDS & !CPUWR & CPUA19 & !CPUA18
#       CPUDS & !CPUWR & CPUA19 & !CPUA17
#       CPUDS & !CPUWR & CPUA19 & !CPUA16
#       CPUDS & !CPUA19 & !CPUA18 & !CPUA17 & !CPUA16 & !SWAP;

CPUHLT.OE = POR;
CPUHLT = POR;

CPURES.OE = POR;
CPURES = POR;

Headers / Connectors

SIMPLE-68008 REV1 CAD.PNG

J1 - 2 port FTDI / TTL Serial

  1. GND
  2. CTS* (in)
  3. +5V
  4. Transmit (out)
  5. Receive (in)
  6. RTS* (out)

Connections to ESP32-TERM Card

ESP32-TERM SIMPLE-68008
Pin Signal Pin Signal
1 GND 1 GND
2 RTS (out) 2 CTS (in)
3 +5V 3 +5V
4 RX (in) 4 TX (out)
5 TX (out) 5 RX (in)
6 CTS (in) 6 RTS (out)

J2 - Input Port

  1. Input 2
  2. Input 5
  3. Input 4
  4. Input 3
  5. Vcc
  6. GND

J3 - Output Port

  1. GND
  2. Vcc
  3. Output 7
  4. Output 6
  5. Output 5
  6. Output 4
  7. Output 3
  8. Output 2

H1 - 5V Power

  • 2x4 header

SIMPLE-68008 H1.PNG

H2-H5 - EPROM/EEPROM Select Jumpers

SIMPLE-68008 REV1 EEP JUMPERS.PNG

  • H2 = EE PIN 31
  • H3 = EE PIN 3
  • H4 = EE PIN 30
  • H5 = EE PIN 29

27SF256

  • 27SF256 is a 28 pin part, socket is 32 pins
    • H2 = Not installed
    • H3-2 to H3-3 = A15 (Vpp on 27SF256, but pin can be either high or low)
    • H4-1 to H4-2 = Vcc
    • H5-2 to H5-3 = CPUA14

EEPROM Jumpers

27040 27020 27010 27512 27256 27128 2764 PIN(32) PIN(28) PIN(28) PIN(32) 2764 27128 27256 27512 27010 27020 27040
VPP VPP VPP N/A N/A N/A N/A 1 N/A N/A 32 N/A N/A N/A N/A VCC VCC VCC
A16 A16 A16 N/A N/A N/A N/A 2 N/A N/A 31 (H2) N/A N/A N/A N/A PGM PGM A18
A15 A15 A15 A15 VPP VPP VPP 3 (H3) 1 28 30 (H4) VCC VCC VCC VCC N/C A17 A17
A12 A12 A12 A12 A12 A12 A12 4 2 27 29 (H5) PGM PGM A14 A14 A14 A14 A14
A7 A7 A7 A7 A7 A7 A7 5 3 26 28 A13 A13 A13 A13 A13 A13 A13
A6 A6 A6 A6 A6 A6 A6 6 4 25 27 A8 A8 A8 A8 A8 A8 A8
A5 A5 A5 A5 A5 A5 A5 7 5 24 26 A9 A9 A9 A9 A9 A9 A9
A4 A4 A4 A4 A4 A4 A4 8 6 23 25 A11 A11 A11 A11 A11 A11 A11
A3 A3 A3 A3 A3 A3 A3 9 7 22 24 OE* OE* OE* OE* OE* OE* OE*
A2 A2 A2 A2 A2 A2 A2 10 8 21 23 A10 A10 A10 A10 A10 A10 A10
A1 A1 A1 A1 A1 A1 A1 11 9 20 22 CE* CE* CE* CE* CE* CE* CE*
A0 A0 A0 A0 A0 A0 A0 12 10 19 21 D7 D7 D7 D7 D7 D7 D7
D0 D0 D0 D0 D0 D0 D0 13 11 18 20 D6 D6 D6 D6 D6 D6 D6
D1 D1 D1 D1 D1 D1 D1 14 12 17 19 D5 D5 D5 D5 D5 D5 D5
D2 D2 D2 D2 D2 D2 D2 15 13 16 18 D4 D4 D4 D4 D4 D4 D4
GND GND GND GND GND GND GND 16 14 15 17 D3 D3 D3 D3 D3 D3 D3

H6 - SRAM Configuration

  • 1-2 = 128KB SRAM
  • 2-3 = 512KB SRAM
  • 128KB and 512KB Parts are about the same price so there's not much point (if buying parts anyway) with going with 512KB part

SIMPLE-68008 Software

Linux Development Environment

SIMPLE-68008 VM Vbox.PNG

  • Using Oracle VM VirtualBox
  • Running Linux Mint
  • The [m68k assembly code toolchain GNU C-Compiler with Binutils and other useful tools for 68000 cross development
  • This is a Makefile based approach to build the toolchain to reduce the build time.
  • The original work was by Steve Moody's page
  • These tools are build:
    • binutils
    • gcc with libs for C/C++/ObjC
    • vasm
    • vbcc
    • vlink
    • newlib

S Record and Hex file manipulation

Initial Test Code

68k-Monitor

Hardware Handshake Notes

*       Set MR2A4 = 1 and MR2A5 = 1 to configure OP0 as RTS output
       MOVE.B #$83,MR1A
       MOVE.B #$27,MR2Aer is ready to
*       receive more data. Note also that the contents of the DUART's
*       output port register are inverted before they are fed to the output
*       pins. That is, to assert RTS* low, it is necessary to load a one
*       into the appropriate bit of the OPR.
*
       MOVE.B #$01,OPR Set OPR0 to assert RTS*

Example Assembly Code

SIMPLE-68008 CPU
RAM Test Passed
> L
Load S-Record
+++++>
> R1000

Example C Code

SIMPLE-68008 CPU
RAM Test Passed
> L
Load S-Record
+++++>
> R2000

String Test C Code

SIMPLE-68008 CPU
RAM Test Passed
> L
Load S-Record
+++++>
> R2000

Test Transmit Interrupt Code

SIMPLE-68008 CPU V1.00
RAM Test Passed
> l
Load S-Record
++++++++++++++++++++>
> r1000
SIMPLE-68008 CPU V1.00
RAM Test Passed
> r1100
42345678S:;<I>?@ABMDPFGHLJKE-6O8QRS00VW8 Z[\C^_`PbUd fghijkVm1o.qrst0vwx0z2
]R7AM:; =>T@ABeDEsGt JKLPNaPsRSsUVWXed[ >` bcdefghijklmnopqrstuvwxyz
23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz
23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz
23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz
23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz
23456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz

Receive Interrupt Test Code

  • S68K_007 GitHub Repository
  • Test interrupt from DUART
    • Using receive character interrupt
  • Runs from RAM
  • Echos back character typed
  • Downloaded as S Records
  • R1000 to run program

60 Hz timer

  • S68K_008 GitHub Repository
  • Make a 60 Hz Counter in memory
  • Use timer in DUART
  • 3.6864 MHz / 16 = 23400
  • 23,400 / 60 (Hz) / 2 per cycle = 1920 count = 0x780
  • Increment a long in 0x604(-0x607)
  • 60 Hz is 0x780 divisor
  • Stop timer to clear timer
  • Restart timer to set up interrupt on next timer edge

Guess a Number Game Code

  • S68K_GAME_01
    • Game to guess a number from 1-99
      • Missing random number generator
    • Structures string and DUART I/O code into separate files
  • S68K_GAME_02
    • Game to guess a number from 1-99
      • Version adds random number generator
    • Slightly less clumsy includes (added a main() stub and moved includes to right after that)

Sample Game with ANSI screen control

  • S68K_GAME_03
  • Move an object around the screen using arrow keys
  • To load it into the S68K_002 monitor you can run the command "L" and then send the run (S record) .run file to the serial port
  • Run the program from the S68K_002 monitor using R2000
    • Output should look like the following:
SIMPLE-68008 CPU

RAM Test Passed

 > l

Load S-Record

++++++++++++++++++++++++++++>

 > r2000
  • Scrren should clear and a '*' will be at the center
  • Arrow keys to move around the '*'
  • Q to quit

ANSI Terminal Driver

Sample Game

S68K-04 Game Snapshot-01.PNG

  • S68K_GAME_04
  • Game framework with basic game elements
  • Written in C
  • Writes to ANSI screen
    • Uses cursor position commands
  • Draws border on the screen
  • Status line at the bottom of the screen
  • Puts '*' at center of the screen
  • Arrow keys move '*' around the playfield

First Person Shooter Game

S68K FPS-06.PNG

  • S68K_GAME_06
  • Runs on ANSI/VT terminal
  • First person shooter
  • Scores of hits/misses
  • Elapsed time since game start
  • Target random movement based on modulo of timer

Enhanced BASIC (Running from SRAM)

SIMPLE-68008 CPU
RAM Test Passed
  • L for Load
> l
Load S-Record
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++>
  • Run at 800
> R800
457232 Bytes free

Enhanced 68k BASIC Version 3.52

Ready
  • Test with short program
10 PRINT "HI"
RUN
HI

Ready

68K Monitor Plus Enhanced BASIC (Running from ROM)

  • Puts S68K_002 - Monitor Code and Enhanced BASIC into a single 32KB ROM
  • Build steps
    • Run make for S68K_002
  • Run make for the Enhanced BASIC which pulls in the S68K_002 code
    • Result is a .hex file
  • EPROM base address = 0x80000
    • 0x80000-0x83FFF - First 16KB reserved addresses for monitor (plenty of room for expansion)
      • Code is from 0x80400-0x80caf (Less than 4KB)
    • 0x84000-0x87FFF - Second 16KB reserves addresses for BASIC (plenty of room for expansion)
      • Code is from 0x84800-0x87D1F (Less than 16KB)
  • Boots into the monitor
  • Run BASIC with 'B' on command line
  • Runs at 38,400 baud
SIMPLE-68008 CPU V1.00
RAM Test Passed
> b
12
490032 Bytes free

Enhanced 68k BASIC Version 3.52

Ready

68000 fig-FORTH V1.0

SIMPLE-68008 CPU V1.00
RAM Test Passed
> l
Load S-Record
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+++++++++++++++++++++++++++>
> r3648

68000 fig-FORTH V1.0
    OK
    OK
    OK
1 2 3     OK
+    OK
+    OK
. 6    OK

Mechanicals

  • Rev 1 card

SIMPLE-68008 REV1 MECHS.PNG

Checkout

Rev 2 Card

  • Fixed DUART TXB and RXA connections (see Rev 1 rework)
  • Added pullup to VPA* line (to make interrupts work - see Rev 1 rework)
  • Add some silkscreen annotations for memory configuration header connections to rear of card
  • Moved R6 up and added more silkscreen near CPU
  • Added R7 resistor and LED to ground on U3-12
    • Access with a write of but D0 to EEPROM address (similar to SWAP bit)
  • Ordered a batch of 10 cards (2024-08-18)

Rev 1 Card

  • VPA needs to be pulled up
    • Add wire U5-39 to U5-40
  • Reset working
    • Reset switch and monitor working
  • Clock working
    • Checked at 8 and 10 MHz
  • EPROM working
  • SRAM working
  • Checked Serial port
    • Not using any XTAL capacitors
  • Serial transmit/receive lines swapped
    • TXB and RXA are swapped on DUART
    • U6 pins 11 and 31 need to be swapped

SIMPLE-68008 J1-Serial.PNG

  • Easiest cuts (on bottom of board)

SIMPLE-68008 Rev1 Serial Cutrs.PNG

  • Cuts as seen from the top side Silkscreen

SIMPLE-68008 J1-Serial PCB 2.PNG

  • 2 Jumpers

SIMPLE-68008 Rev1 Serial Jumpers P1579-720px.jpg

  • Alternative cut (harder due to space and being on top of board)

SIMPLE-68008 J1-Serial PCB.PNG

Assembly Sheet

Rev 2

Rev 1

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