Z80-MBC2 Build Notes

Sourced PCB

• ebay - bare PCB $8
  • Arrived in a couple of days

Reference Docs

• An Easy to Build Real Homemade Computer: Z80-MBC2! - Instructable was helpful
• Hackaday project with files

Build Notes

• All through hole construction
• Build took less than 2 hours
• Used mostly junk box parts
  • 20 MHz Z80
• Purchased alternate SRAM
  • AS6C1008-55PIN
• Purchased DIP machined sockets (I usually go cheaper but these were very nice)
• Forgot to buy SIP resistors
  • Made my own SIP resistors
  • Pin 1 (boxed pin on silkscreen is the common
  • Used 1/8W resistors vertically mounted
• 5mm LEDs fit into 3mm hole spacing
  • I didn't have a 3mm Blue so I used 5mm

Negatives

• Ref des are not top-bottom or left-right
  • PDF Assembly drawing text is not searchable
  • Struggled to find some of the resistors on the PCB
• Serial port marking correlated to the FTDI card end not referenced from card internal

Programming THE ATMEGA32

• IOS-LITE build (no SD card support)
• Was able to use ATProgHead ICSP 2x3 cable running Arduino as ISP to burn bootloader but not program the code
• Could not use any of my FTDI cards for serial programming since they have RTS/CTS but not DTR
  • Most programmer setups in Arduino work just fine with RTS since both are usually pulled, but not the MightyCore
  • This is speculation as to why but I am able to program Screwduino cards just fine
• Used TL866ii to program ATMEGA32 fuses
  • The Fuse bits should be: High Byte 0xD6, Low Byte 0xAF, Lock Byte 0xCF.
  • Reference: Setting AVR Fuse Bits
  • If you use the programmer defaults it sets the clock to 1 MHz which gives a serial port rate of 600 baud (told me I needed to fix the fuses).

• Found path in dump in Arduino IDE:

Arduino: 1.8.13 (Windows 10), Board: "ATmega32, Yes (UART0), EEPROM retained, Standard pinout, BOD 2.7V, LTO disabled, External 16 MHz"
Sketch uses 28642 bytes (88%) of program storage space. Maximum is 32256 bytes.
Global variables use 1213 bytes (59%) of dynamic memory, leaving 835 bytes for local variables. Maximum is 2048 bytes.
C:\Users\HPz420\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino18/bin/avrdude -CC:\Users\HPz420\AppData\Local\Arduino15\packages\MightyCore\hardware\avr\2.1.3/avrdude.conf -v -patmega32 -carduino -PCOM23 -b115200 -D -Uflash:w:C:\Users\HPz420\AppData\Local\Temp\arduino_build_883457/S220618_IOS-LITE-Z80-MBC2.ino.hex:i 

Software