RETRO-EP4

RETRO-EP4 FPGA Card

I love Grant Searle's Multicomp project. It lets you create 6502, Z80, 6809 Retrocomputers of the late 1970s era. This card provides all of the connections needed.

Grant's original design used an EP2 but that's not compatible with the latest version Altera/Intel Quartus.This upgrades to the newer EP4CE6 FPGA. We've done the work of porting the Multicomp to this card.

Features

Here's the features list:

• 6 bit video on VGA
  • 2:2:2 R:G:B
• PS/2 connector for keyboard
• 512KB of SRAM for banked use in CP/M
• Mount for inexpensive FTDI USB to serial converter
• SD Card
• Headers for extra I/O
• DC power jack

VGA - Ideal Drive 2:2:2 Case

• FPGA has a 3.3V driver which can drive 8 mA
• Ideal case drive current
  • 0.7V into 75 Ohms = 9.33 mA
• R-2R values
  • Ideal resistor values are 417.9 ohms and 835.7 ohms
  • Standard value 1% resistors
  • 1% standard values are 422 (Mouser), 845 (Mouser) Ohms
    • Get closest values
    • 0V, 0.228V, 0.460V, 0.693V
• Voltage steps are:

• Current steps are:

Schematics

• Rev X1 schematic
• Rev X2 schematic

Multicomp Builds

• Github repository for Multicomp builds

Pin List

set_location_assignment PIN_23 -to clk
set_location_assignment PIN_85 -to driveLED
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to driveLED
set_location_assignment PIN_125 -to n_reset
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to n_reset
set_location_assignment PIN_127 -to ps2Clk
set_location_assignment PIN_126 -to ps2Data
set_location_assignment PIN_132 -to rxd1
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to rxd1
set_location_assignment PIN_128 -to txd1
set_location_assignment PIN_129 -to rts1
set_location_assignment PIN_112 -to videoR1
set_location_assignment PIN_113 -to videoR0
set_location_assignment PIN_114 -to videoG1
set_location_assignment PIN_115 -to videoG0
set_location_assignment PIN_124 -to videoB1
set_location_assignment PIN_120 -to videoB0
set_location_assignment PIN_119 -to hSync
set_location_assignment PIN_121 -to vSync
set_location_assignment PIN_58 -to sdCS
set_location_assignment PIN_60 -to sdSCLK
set_location_assignment PIN_59 -to sdMISO
set_location_assignment PIN_55 -to sdMOSI
set_location_assignment PIN_68 -to n_sRamCS
set_location_assignment PIN_50 -to n_sRamOE
set_location_assignment PIN_75 -to n_sRamWE
set_location_assignment PIN_65 -to sramAddress[0]
set_location_assignment PIN_64 -to sramAddress[1]
set_location_assignment PIN_67 -to sramAddress[2]
set_location_assignment PIN_66 -to sramAddress[3]
set_location_assignment PIN_69 -to sramAddress[4]
set_location_assignment PIN_74 -to sramAddress[5]
set_location_assignment PIN_77 -to sramAddress[6]
set_location_assignment PIN_76 -to sramAddress[7]
set_location_assignment PIN_83 -to sramAddress[8]
set_location_assignment PIN_80 -to sramAddress[9]
set_location_assignment PIN_34 -to sramAddress[10]
set_location_assignment PIN_33 -to sramAddress[11]
set_location_assignment PIN_38 -to sramAddress[12]
set_location_assignment PIN_39 -to sramAddress[13]
set_location_assignment PIN_42 -to sramAddress[14]
set_location_assignment PIN_51 -to sramAddress[15]
set_location_assignment PIN_52 -to sramAddress[16]
set_location_assignment PIN_53 -to sramAddress[17]
set_location_assignment PIN_54 -to sramAddress[18]
set_location_assignment PIN_71 -to sramData[0]
set_location_assignment PIN_70 -to sramData[1]
set_location_assignment PIN_73 -to sramData[2]
set_location_assignment PIN_72 -to sramData[3]
set_location_assignment PIN_43 -to sramData[4]
set_location_assignment PIN_44 -to sramData[5]
set_location_assignment PIN_46 -to sramData[6]
set_location_assignment PIN_49 -to sramData[7]
set_location_assignment PIN_3 -to ledOut8[0]
set_location_assignment PIN_7 -to ledOut8[1]
set_location_assignment PIN_10 -to ledOut8[2]
set_location_assignment PIN_11 -to ledOut8[3]
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to sdMISO
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to ps2Data
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to ps2Clk

RETRO-EP4 Assembly Sheet

• RETRO-EP4 Rev X2 Assembly Sheet