Table of Contents
Partial Emulation of MC6850 ACIA
Introduction
When using the ACIA in the popular no-parity, 8-data, and 1 stop bit mode and when baud clock is integer multiple of system clock, the ACIA design simplifies significantly so it can be emulated with a small CPLD. This repurposed FRR512K board describes such emulation.
Features
- Serial port setting of 115200, 8-data, 1-stop, and no parity
- Serial baud must be integer multiple of system clock
- Implemented in EPM7064SLC44
- Re-purposed FRR512K board
Design Information
- PDF schematic of the CPLD design file
Engineering change
Interrupt
- Flash-pin30 (Bank3) to T7 (nINT)
Serial Connections
- SCL to serial hdr pin2 (TxD)
- SDA to serial hdr pin3(RxD)
- serial hdr pin5 to GND
- serial hdr pin1 (nRTS) to flash-pin22(nROMCS)
Data bus connections
- Flash-pin1 (Bank4) to Flash-pin 18 (D4)
- Flash-pin2 (Bank2) to Flash-pin19(D5)
- Flash-pin3(Bank1) to Flash-pin20(D6)
Components Populated
- P1, RC2014 bus connector,
- U1, EPM7064SLC44
- P3, CPLD programming header
- P21, 6-pin serial port header
- U2, Oscillator
- R1,R4, 4.7K resistors
- 100 ohm resistor between T8 and T37
- Bypass capacitors
