LB-6809-01

Features

• 68B09 CPU
• 8 MHZ crystal on card
  • CPU runs at 2 MHz
• Reset switch/power monitor
• Address decoder PLD drives RAM/ROM/IO chip selects
• 100x50mm card

Memory Map

• 0x0000-0x7FFF 32KB SRAM
• 0x8000-0x9FFF Free Space (8KB)
• 0xA000-0xBFFF Serial (ACIA)
• 0xC000-0xFFFF 16KB EPROM

Design

68B09 CPU

• 8 MHz clock
  • Runs effectively at 2 MHz

CPU - Rev 2

CPU - Rev 1

CPU Timing

Crystal - Rev 2

• Uses CPU internal oscillator

Oscillator - Rev 1

• 8 MHz oscillator for 2 MHz operation

PLD

• ATF16V8B part
• TL866ii Plus Programmer

PLD on Card Rev 2

PLD on Card Rev 1

• Wire added (Rev 1) from E pin of CPU to PLD pin 7
  • Signal name VPB

PLD Listing

Name       LB-6809-01_PLD;
Partno     ATF16V8B;
Date       08/19/24;
Revision   01;
Designer   DOUG G;
Company    LAND BOARDS LLC;
Assembly   LB680901_U2;
Location   Rustbelt, US;
Device     G16V8;

/*
*/


/* Control inputs */
PIN    1   = CLK;
PIN    2   = CPUA12;
PIN    3   = CPUA13;
PIN    4   = CPUA14;
PIN    5   = CPUA15;
PIN    6   = CPUREAD;
PIN    7   = VPB;		/* Added as wire on Rev 1 PCB	*/
PIN    8   = VPA;
PIN    9   = VDA;

/* Address Decode and Chip Select outputs */
PIN    12  = !ROMCS;
PIN    13  = !IOCS;
PIN    14  = !MEMRD;
PIN    16  = !RAMCS;
PIN    18  = RDY;

ROMCS = CPUA15 & CPUA14 & VPB;

RAMCS = !CPUA15 & VPB
#        CPUA15 & !CPUA14 & !CPUA13 & VPB;

IOCS = CPUA15 & !CPUA14 & CPUA13 & VPB;

RDY = VPB;

MEMRD = CPUREAD & VPB;

Backplane connector

Software

• SIMPLE-6809 Software
• asm6809 - portable cross assembler targeting the Motorola 6809
  • Features arbitrarily complex expressions (with most C-style operators available), forward references, macro expansion and conditional assembly
  • Output formats are: Raw binary, DragonDOS binary, CoCo RS-DOS (or "DECB") binary, Motorola SREC, Intel HEX.
  • asm6809 Manual

Build 6809 Assembly Code

• Run asm6809in Windows CMD prompt window

[path_to_asm6809.exe_program\asm6809 loop.asm -H -o loop.hex

Mechanicals

Rev 2

Rev 1

Checkout

Rev 2 Checkout

• Built
• Worked with NOP Tester

Rev 2 PCB Changes from Rev 1

• Add U1-34 to U2-7 (VPB/E)
• Eliminate oscillator
  • Add 8 MHz crystal/caps
  • Cheaper and easier to find
• Add 4.7K pullup to U1-40 (ABORT*/HALT) line
• Change resistor values to lighten up Iol
• Beef up power plane connections to J1 and CPU/cap
• Move reset switch to the top of the board (where the oscillator used to be)

Rev 1 Checkout Notes

• Did not build
• Add wire U1-34 to U2-7 (VPB/E)
• Ground XTAL pin on CPU U1-39 (to U1-1 = GND)
• Use BOM for resistor values, not silkscreen
• Add 4.7K pullup to ABORT* line

Assembly Sheet

Rev 2

• Interactive BOM

Rev 1

• Use BOM for resistor values, not silkscreen
• Interactive BOM