Wichit Sirichote, wichit.sirichote@gmail.com
Build a microcomputer training kit with the Motorola 6809 CPU. Updated monitor version3, User Manual and Programming book.!
I got suggestion from Didier to design the trainer kit with 6809 or 6309 microprocessor. So I spent my free time design this kit. The kit uses Motorola 68B09 as the CPU. I added the UART chip, 6850 ACIA. The circuit is simple and use small number of components. All decoder logics are placed in PLD chip. This makes the circuit is very easy to build. I found cc09 c compiler for 6809. The monitor was developed using c and assembly code. The main clock frequency is 4.9152MHz. UART chip uses E clock, 4.9152MHz/4 as the TXD/RXD clock. The prescaler is 64, so the UART will produce 19,200 bit/s rate. The 6809 has long branch using 16 bit offset. One of the monitor key provides 16-bit HEX calculator. Students can use it for finding the 8-bit or 16-bit offset. For low level coding, we can use hex key to enter and test the program. For c programming, we can use UART for S19 file downloading easily.
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| Figure 1: Motorola 6809 Microprocessor kit 2017 |
Hardware descriptions:
U5 is the Motorola 68B09 CPU. The 4.9152MHz is generated by onchip oscillator with internal frequency 1.228MHz for CPU operations. NMI, HALT, IRQ, FIRQ are pull-up to logic 1 with R2. Only E and R/W and A0,A1, A10-A15 are used for memory decoding.
U1 is 32kB EPROM, 27C256. The address space for EPROM is decoded at 0xC000-0xFFFF.
U2 is 32kB static RAM, 62256. The RAM space is located at 0x0000-0x7FFF. Zero page is located at 0x0000-0x00FF. User program can be tested from address 0x0200.
U4, memory and I/O spaces decoder chip is made with GAL16V8D. It provides chip selected signals for memory and I/O chips.
U3, the 20-pin 89C2051 microcontroller chip produces 10ms tick. SW1 selects between 10ms tick or manual IRQ button.
U6 is 6850 ACIA, UART. The shift clock is derived from E clock, 1228800Hz. Internal prescaler is 64. Thus the bit rate will be 19200 bit/s.
U12, 74HC541 is 8-bit input port (PORT0). Six bits, PA0-PA5 are input signals of the row keypad.
U10, 74HC573 is 8-bit output port (PORT2). The 8-bit output drives the 7-segment LED directly. No current limit resistor. U11 (PORT1) drives 6-digit common cathode pin. The brightness is controlled by software controlled PWM. PC7 is speaker output for beep signal.
U13, 74HC573 is 8-bit output port for 8-bit binary number display. D13 lifts the forward biasing for proper brightness. JR1 is 16-pin socket for text LCD interface. U14, HIN232 converts TTL level to RS232 level.
Q2, KIA7042 is reset chip for power brownout.
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| Figure 3: Hardware schematic (click to enlarge) |
Hardware Features:
-CPU: Motorola 68B09, 8-bit Microprocessor @1.2288MHz clock
-Memory: 32kB RAM, 16kB EPROM
-Memory and I/O Decoder chip: Programmable Logic Device GAL16V8D
-Display: high brightness 6-digit 7-segment LED
-Keyboard: 36 keys
-RS232 port: 6850 ACIA 19200 bit/s 8n1
-Debugging LED: 8-bit GPIO1 LED at location $8000
-Tick: 10ms tick produced by 89C2051 for time trigger experiment
-Text LCD interface: direct CPU bus interface text LCD
-Brownout reset: KIA7042 reset chip for power brownout reset
-Expansion header: 40-pin header
