PDP-8 Front Panel

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PDP-8 P458-720pxV.jpg


  • 50 pin connector
    • 2x25 Pinout matches RETRO-EP4CE15 Card pins (1:1 cable)
    • Some unused pins - wired to +3.3V/GND for connecting other cards
  • 12 Value LEDs (DB0-11) - octal format
    • Display options: Program Counter (PC), Memory Address, Memory Data, Accumulator
  • 12 Load Value Slide Switches (SL0-11) - octal format
    • Enter values: PC, Memory Address, Memory Data, Accumulator
  • LNK - Link value slide switch
  • DISP - Display 12 Value LEDs select pushbutton
    • Cycles between LEDs displaying PC, Memory Address, Memory Data, Accumulator
  • Pushbutton Switches
    • STEP pushbutton - Increment PC
    • LDPC pushbutton - Load PC from Value Slide Switches
    • DEP pushbutton - Store value from Value Slide Switches to memory
    • LDA pushbutton - Store value from Value Slide Switches to Accumulator
    • RES - Reset pushbutton - Resets CPU
    • PB1 - spare pushbutton
  • 4 DISP LEDs - Cycle between 12 LEDs source with DISP pushbutton
    • PC - 12 LEDs display Program Counter value
    • MADR - 12 LEDs display Memory Address value
    • MD - 12 LEDs display Memory Data value
    • AC - 12 LEDs display Accumulator value
  • LINK LED - Displays Link value
  • RUN LED - Running program
  • RUN/HALT slide switch
  • PWR - Power LED
  • 95x95mm form factor
  • (4) 6-32 mounting holes

PDP-8 FPGA Design[edit]

Runs with Tom Almy's PDP-8 and OpenCores PDP-8 FPGA designs.

Tom Almy's PDP-8[edit]

OpenCores PDP-8[edit]

J1 Connector[edit]

  • Extra power and ground pins (not on RETRO-EP4CE15 Card)
    • Pins 3,4 = GND
    • Pins 5-8 = VCC
    • Pin 9 = N/C

J1 to RETRO-EP4CE15 Pin Mapping[edit]

PDP-8F FrontPanel Conn Map RETRO-EP4CE15 Both.PNG

Real PDP-8/F Front Panel[edit]

PDP-8F FrontPanel 720px.jpg

Pin List for Tom Almy FPGA Build[edit]

set_global_assignment -name FAMILY "Cyclone IV E"
set_global_assignment -name DEVICE EP4CE15F23C8
set_global_assignment -name TOP_LEVEL_ENTITY pdp8
set_global_assignment -name ORIGINAL_QUARTUS_VERSION 18.1.0
set_global_assignment -name PROJECT_CREATION_TIME_DATE "13:56:19  MARCH 15, 2021"
set_global_assignment -name LAST_QUARTUS_VERSION "20.1.0 Lite Edition"
set_global_assignment -name PROJECT_OUTPUT_DIRECTORY output_files
set_global_assignment -name MIN_CORE_JUNCTION_TEMP 0
set_global_assignment -name MAX_CORE_JUNCTION_TEMP 85
set_global_assignment -name ERROR_CHECK_FREQUENCY_DIVISOR 1
set_global_assignment -name NOMINAL_CORE_SUPPLY_VOLTAGE 1.2V
set_global_assignment -name PARTITION_NETLIST_TYPE SOURCE -section_id Top
set_global_assignment -name PARTITION_COLOR 16764057 -section_id Top
set_global_assignment -name SMART_RECOMPILE ON
set_global_assignment -name STRATIX_DEVICE_IO_STANDARD "3.3-V LVTTL"
# Clock, reset button
set_location_assignment PIN_T2 -to clk
set_location_assignment PIN_K22 -to btnCpuReset
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to btnCpuReset
# Run Switch/LED
set_location_assignment PIN_H22 -to runSwitch
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to runSwitch
set_location_assignment PIN_F21 -to runLED
# Serial
set_location_assignment PIN_B13 -to RsRx
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to RsRx
set_location_assignment PIN_B10 -to RsTx
# PS/2
set_location_assignment PIN_R1 -to io_ps2Clk
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to io_ps2Clk
set_location_assignment PIN_R2 -to io_ps2Data
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to io_ps2Data
set_location_assignment PIN_A17 -to o_vid_blu[1]
set_location_assignment PIN_B17 -to o_vid_blu[0]
set_location_assignment PIN_A16 -to o_vid_grn[1]
set_location_assignment PIN_B16 -to o_vid_grn[0]
set_location_assignment PIN_A15 -to o_vid_red[1]
set_location_assignment PIN_B15 -to o_vid_red[0]
set_location_assignment PIN_B18 -to o_vid_hSync
set_location_assignment PIN_A18 -to o_vid_vSync
# 12 Slide switches
set_location_assignment PIN_AB14 -to sw[0]
set_location_assignment PIN_AB16 -to sw[1]
set_location_assignment PIN_AB18 -to sw[2]
set_location_assignment PIN_AB19 -to sw[3]
set_location_assignment PIN_AA20 -to sw[4]
set_location_assignment PIN_W21 -to sw[5]
set_location_assignment PIN_V22 -to sw[6]
set_location_assignment PIN_U22 -to sw[7]
set_location_assignment PIN_R22 -to sw[8]
set_location_assignment PIN_N22 -to sw[9]
set_location_assignment PIN_M22 -to sw[10]
set_location_assignment PIN_L22 -to sw[11]
# 12 LEDs
set_location_assignment PIN_J21 -to dispLEDs[11]
set_location_assignment PIN_L21 -to dispLEDs[10]
set_location_assignment PIN_M21 -to dispLEDs[9]
set_location_assignment PIN_N21 -to dispLEDs[8]
set_location_assignment PIN_P21 -to dispLEDs[7]
set_location_assignment PIN_U21 -to dispLEDs[6]
set_location_assignment PIN_W22 -to dispLEDs[5]
set_location_assignment PIN_Y21 -to dispLEDs[4]
set_location_assignment PIN_AA19 -to dispLEDs[3]
set_location_assignment PIN_AA18 -to dispLEDs[2]
set_location_assignment PIN_AA16 -to dispLEDs[1]
set_location_assignment PIN_AA14 -to dispLEDs[0]
# Status/Operation LEDs
set_location_assignment PIN_K21 -to linkLED
set_location_assignment PIN_Y22 -to dispMDLED
set_location_assignment PIN_AA17 -to dispMALED
set_location_assignment PIN_AA15 -to dispPCLED
set_location_assignment PIN_R21 -to dispACLED
set_location_assignment PIN_H21 -to lnkSwitch
# Pushbuttons
set_location_assignment PIN_AB17 -to stepPB
set_location_assignment PIN_V21 -to depPB
set_location_assignment PIN_AB20 -to ldPCPB
set_location_assignment PIN_P22 -to ldACPB
set_location_assignment PIN_AB15 -to dispPB

Pin List for OpenCores Build[edit]

  • PB1 is EXAM pushbutton
set_global_assignment -name FAMILY "Cyclone IV E"
set_global_assignment -name DEVICE EP4CE15F23C8
set_global_assignment -name TOP_LEVEL_ENTITY pdp8_top
set_global_assignment -name ORIGINAL_QUARTUS_VERSION 11.1
set_global_assignment -name PROJECT_CREATION_TIME_DATE "19:28:47  OCTOBER 30, 2013"
set_global_assignment -name LAST_QUARTUS_VERSION "20.1.0 Lite Edition"
set_global_assignment -name MIN_CORE_JUNCTION_TEMP 0
set_global_assignment -name MAX_CORE_JUNCTION_TEMP 85
set_global_assignment -name ERROR_CHECK_FREQUENCY_DIVISOR 1
set_global_assignment -name PARTITION_NETLIST_TYPE SOURCE -section_id Top
set_global_assignment -name PARTITION_COLOR 16764057 -section_id Top
set_global_assignment -name STRATIX_DEVICE_IO_STANDARD "3.3-V LVTTL"
# Clock and reset
set_location_assignment PIN_T2 -to CLOCK_50
set_location_assignment PIN_K22 -to reset_n
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to reset_n
# PS/2
set_location_assignment PIN_R1 -to io_PS2_CLK
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to io_PS2_CLK
set_location_assignment PIN_R2 -to io_PS2_DAT
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to io_PS2_DAT
set_location_assignment PIN_B10 -to TTY1_TXD_Ser
set_location_assignment PIN_B13 -to TTY1_RXD_Ser
set_location_assignment PIN_A10 -to TTY1_RTS_ser
set_location_assignment PIN_A13 -to TTY1_CTS_ser
set_location_assignment PIN_B22 -to serSelect
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to serSelect
# Video
set_location_assignment PIN_B15 -to o_videoR0
set_location_assignment PIN_A15 -to o_videoR1
set_location_assignment PIN_B16 -to o_videoG0
set_location_assignment PIN_A16 -to o_videoG1
set_location_assignment PIN_B17 -to o_videoB0
set_location_assignment PIN_A17 -to o_videoB1
set_location_assignment PIN_B18 -to o_hSync
set_location_assignment PIN_A18 -to o_vSync
# SD Card
set_location_assignment PIN_B19 -to sdCS
set_location_assignment PIN_B20 -to sdCLK
set_location_assignment PIN_A19 -to sdDI
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to sdDI
set_location_assignment PIN_A20 -to sdDO
set_location_assignment PIN_B14 -to sdCD
set_instance_assignment -name WEAK_PULL_UP_RESISTOR ON -to sdCD
# Front Panel LEDs
set_location_assignment PIN_F21 -to RUN_LED
set_location_assignment PIN_AA15 -to PC_LED
set_location_assignment PIN_R21 -to AC_LED
set_location_assignment PIN_AA17 -to MADR_LED
set_location_assignment PIN_Y22 -to MD_LED
set_location_assignment PIN_K21 -to LINK_LED
# Front Panel Pushbuttons and Slide Switches
set_location_assignment PIN_P22 -to LDA_PB
set_location_assignment PIN_AB20 -to LDPC_PB
set_location_assignment PIN_V21 -to DEP_PB
set_location_assignment PIN_AB17 -to STEP_PB
set_location_assignment PIN_H21 -to LINK_SS
set_location_assignment PIN_AB15 -to DISP_PB
set_location_assignment PIN_J22 -to EXAM_PB
set_location_assignment PIN_H22 -to RUN_SS
# 12 LEDs
set_location_assignment PIN_AA14 -to OUT12_LEDs[0]
set_location_assignment PIN_AA16 -to OUT12_LEDs[1]
set_location_assignment PIN_AA18 -to OUT12_LEDs[2]
set_location_assignment PIN_AA19 -to OUT12_LEDs[3]
set_location_assignment PIN_Y21 -to OUT12_LEDs[4]
set_location_assignment PIN_W22 -to OUT12_LEDs[5]
set_location_assignment PIN_U21 -to OUT12_LEDs[6]
set_location_assignment PIN_P21 -to OUT12_LEDs[7]
set_location_assignment PIN_N21 -to OUT12_LEDs[8]
set_location_assignment PIN_M21 -to OUT12_LEDs[9]
set_location_assignment PIN_L21 -to OUT12_LEDs[10]
set_location_assignment PIN_J21 -to OUT12_LEDs[11]
# 12 Slide switches
set_location_assignment PIN_AB14 -to SW12_SS[0]
set_location_assignment PIN_AB16 -to SW12_SS[1]
set_location_assignment PIN_AB18 -to SW12_SS[2]
set_location_assignment PIN_AB19 -to SW12_SS[3]
set_location_assignment PIN_AA20 -to SW12_SS[4]
set_location_assignment PIN_W21 -to SW12_SS[5]
set_location_assignment PIN_V22 -to SW12_SS[6]
set_location_assignment PIN_U22 -to SW12_SS[7]
set_location_assignment PIN_R22 -to SW12_SS[8]
set_location_assignment PIN_N22 -to SW12_SS[9]
set_location_assignment PIN_M22 -to SW12_SS[10]
set_location_assignment PIN_L22 -to SW12_SS[11]
# SRAM (not used)
set_location_assignment PIN_F1 -to n_sRamCS
set_location_assignment PIN_J2 -to n_sRamOE
set_location_assignment PIN_B4 -to n_sRamWE
set_location_assignment PIN_E1 -to sramData[0]
set_location_assignment PIN_C1 -to sramData[1]
set_location_assignment PIN_B1 -to sramData[2]
set_location_assignment PIN_B3 -to sramData[3]
set_location_assignment PIN_B2 -to sramData[4]
set_location_assignment PIN_C2 -to sramData[5]
set_location_assignment PIN_D2 -to sramData[6]
set_location_assignment PIN_F2 -to sramData[7]
set_location_assignment PIN_H1 -to sramAddress[0]
set_location_assignment PIN_J1 -to sramAddress[1]
set_location_assignment PIN_M1 -to sramAddress[2]
set_location_assignment PIN_N1 -to sramAddress[3]
set_location_assignment PIN_P1 -to sramAddress[4]
set_location_assignment PIN_P2 -to sramAddress[5]
set_location_assignment PIN_N2 -to sramAddress[6]
set_location_assignment PIN_M2 -to sramAddress[7]
set_location_assignment PIN_H2 -to sramAddress[8]
set_location_assignment PIN_A3 -to sramAddress[9]
set_location_assignment PIN_A4 -to sramAddress[10]
set_location_assignment PIN_C3 -to sramAddress[11]
set_location_assignment PIN_A5 -to sramAddress[12]
set_location_assignment PIN_A6 -to sramAddress[13]
set_location_assignment PIN_A7 -to sramAddress[14]
set_location_assignment PIN_A8 -to sramAddress[15]
set_location_assignment PIN_B7 -to sramAddress[16]
set_location_assignment PIN_B6 -to sramAddress[17]
set_location_assignment PIN_B5 -to sramAddress[18]
set_location_assignment PIN_C4 -to sramAddress[19]
# SDRAM (not used)
set_location_assignment PIN_Y6 -to sdRamClk
set_location_assignment PIN_W6 -to sdRamClkEn
set_location_assignment PIN_AA4 -to n_sdRamCas
set_location_assignment PIN_AA3 -to n_sdRamCe
set_location_assignment PIN_AB3 -to n_sdRamRas
set_location_assignment PIN_AB4 -to n_sdRamWe
set_location_assignment PIN_V2 -to sdRamAddr[0]
set_location_assignment PIN_V1 -to sdRamAddr[1]
set_location_assignment PIN_U2 -to sdRamAddr[2]
set_location_assignment PIN_U1 -to sdRamAddr[3]
set_location_assignment PIN_V3 -to sdRamAddr[4]
set_location_assignment PIN_V4 -to sdRamAddr[5]
set_location_assignment PIN_Y2 -to sdRamAddr[6]
set_location_assignment PIN_AA1 -to sdRamAddr[7]
set_location_assignment PIN_Y3 -to sdRamAddr[8]
set_location_assignment PIN_V5 -to sdRamAddr[9]
set_location_assignment PIN_W1 -to sdRamAddr[10]
set_location_assignment PIN_Y4 -to sdRamAddr[11]
set_location_assignment PIN_V6 -to sdRamAddr[12]
set_location_assignment PIN_Y1 -to sdRamAddr[13]
set_location_assignment PIN_W2 -to sdRamAddr[14]
set_location_assignment PIN_AA10 -to sdRamData[0]
set_location_assignment PIN_AB9 -to sdRamData[1]
set_location_assignment PIN_AA9 -to sdRamData[2]
set_location_assignment PIN_AB8 -to sdRamData[3]
set_location_assignment PIN_AA8 -to sdRamData[4]
set_location_assignment PIN_AB7 -to sdRamData[5]
set_location_assignment PIN_AA7 -to sdRamData[6]
set_location_assignment PIN_AB5 -to sdRamData[7]
set_location_assignment PIN_Y7 -to sdRamData[8]
set_location_assignment PIN_W8 -to sdRamData[9]
set_location_assignment PIN_Y8 -to sdRamData[10]
set_location_assignment PIN_V9 -to sdRamData[11]
set_location_assignment PIN_V10 -to sdRamData[12]
set_location_assignment PIN_Y10 -to sdRamData[13]
set_location_assignment PIN_W10 -to sdRamData[14]
set_location_assignment PIN_V11 -to sdRamData[15]

PDP-8 Front Panel Assembly Sheet[edit]

PDP-8 Front Panel Assembly Sheet