SIMPLE-Z80

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CPU-z80 REV1 FRONT (BLK).png

Features

Memory Map

  • 0x0000-0x1FFF 8KB ROM
  • 0x2000-0xFFFF 56KB SRAM
  • I/O
    • 0x00-0x7F - Free
    • 0x80-0x81 - Serial port (ACIA)

Chip Set

SimpleZ80 Chipset.jpg

Design

  • CPU

SIMPLE-Z80 U2 CPU.PNG

  • EPROM

SIMPLE-Z80 U6 EPROM.PNG

  • SRAM

SIMPLE-Z80 U4 SRAM.PNG

  • ACIA

SIMPLE-Z80 U3 ACIA.PNG

  • Clock

SIMPLE-Z80 U5 CLK.PNG

Headers / Connectors

SIMPLE-Z80 REV1 CAD.PNG

J1 - RS-232 Serial

  • DB-9 Male
  • Pinout
  1. N/C
  2. Receive
  3. Transmit
  4. Loop to pin 6
  5. GND
  6. Loop to pin 4
  7. RTS
  8. N/C
  9. N/C

J2/J5 - EPROM/EEPROM Select Jumpers

SIMPLE-Z80 J2 J5.PNG

EEPROM Pin Table

27512 27256 27SF256 28C256 27128 2764 28C64 PIN PIN 2764 28C64 27128 28C256 27SF256 27256 27512
A15 VPP VPP A14 VPP VPP N/C 1 28 VCC VCC VCC VCC VCC VCC VCC
A12 A12 A12 A12 A12 A12 A12 2 27 PGM WE* PGM WE* A14 A14 A14
A7 A7 A7 A7 A7 A7 A7 3 26 A13 N/C A13 A13 A13 A13 A13
A6 A6 A6 A6 A6 A6 A6 4 25 A8 A8 A8 A8 A8 A8 A8
A5 A5 A5 A5 A5 A5 A5 5 24 A9 A9 A9 A9 A9 A9 A9
A4 A4 A4 A4 A4 A4 A4 6 23 A11 A11 A11 A11 A11 A11 A11
A3 A3 A3 A3 A3 A3 A3 7 22 OE* OE* OE* OE* OE* OE* OE*
A2 A2 A2 A2 A2 A2 A2 8 21 A10 A10 A10 A10 A10 A10 A10
A1 A1 A1 A1 A1 A1 A1 9 20 CE* CE* CE* CE* CE* CE* CE*
A0 A0 A0 A0 A0 A0 A0 10 19 D7 D7 D7 D7 D7 D7 D7
D0 D0 D0 D0 D0 D0 D0 11 18 D6 D6 D6 D6 D6 D6 D6
D1 D1 D1 D1 D1 D1 D1 12 17 D5 D5 D5 D5 D5 D5 D5
D2 D2 D2 D2 D2 D2 D2 13 16 D4 D4 D4 D4 D4 D4 D4
GND GND GND GND GND GND GND 14 15 D3 D3 D3 D3 D3 D3 D3

J3 - FTDI / TTL Serial

SIMPLE-Z80 J3 FTDI.PNG


  1. GND
  2. N/C
  3. +5V
  4. Transmit (out)
  5. Receive (in)
  6. RTS* (out)

J4 - 5V Power

  • 2x4 header

SIMPLE-Z80 J4 PWR.PNG

First Unit Checkout

  • PCB

SIMPLE-Z80 P1090181-720px.jpg

Install Sockets

  • Machined pin sockets

Install Passives

Power

  • Install 2x4 at J4
  • Power card via J4 with 5V
  • Check power pins on parts

Clock

  • Install Clock parts
    • Install R2, R3
    • Install C5, C6
    • Install 7.3728 MHz crystal
    • Install 74HC04 at U5
  • Measure clock at U5-4
    • 7.32 MHz clock - looks good

Reset

  • Do not install U8 Power Monitor
    • Reset button gets stretched by Power Monitor U9
  • Install pushbutton switch SW1
  • Measure reset at Z80 U2 pin marked RST on silkscreen

SIMPLE-Z80 P1090202-720PX.jpg

EPROM

  • U6 = SST27C256 EEPROM
    • 32 KB part
    • Using first 16KB of EEPROM
    • J2 EEPROM pin 1 = VPP = VCC or GND
      • Jumper J2:2-3
    • J5 EEPROM pin 27 = A14 = GND
      • Jumper J5:2-3

EEPROM Programming

  • Program using TL-866ii plus programmer
  • File = ROM.HEX - I/O routines plus BASIC
  • Set offsets for 27SF256 part
    • Part is 32 KB
    • hex files is 16 KB
  • Set From File Start Addr(Hex) to 00000
  • To Buffer Start Addr(Hex) to 00000

SIMPLE-6809 Programmer Offsets.PNG

  • Got Device ID error
  • Turn off ID check

SIMPLE-6502 TL866Plus Program.png

  • Device programmed/verified

Install CPU, ROM, RAM, ACIA

  • U1 - Do not install MAX232 yet

Test FTDI Serial

Test RS-232 Serial

  • With MAX232
  • Install DB-9 Male
  • Holes don't line up well, but 4-40 screws can fit
  • Connected to FTDI-49MM and DCE cards

FTDI DCE P1090192-720PXV.jpg

  • Works

SIMPLE-6809 P1090197-720PXV.jpg

Software

  • ROM.HEX - ROM file
  • Nascom Computer BASIC modified to remove all hardware-specific code

Source files

  • intmini.asm - the interupt driven mini startup program needed to boot into BASIC
  • basic.asm - BASIC 4.7b - a conversion of Microsoft BASIC 4.7, as used on the Nascom computers (see below for details)

Output files

  • INTMINI.HEX
  • BASIC.HEX
  • ROM.HEX - the complete 8K ROM ready for burning to an EPROM - the unused contents are filled with FF values.
  • Within the ROM, the serial handler is first (starting at address 0000H), followed by the BASIC interpreter (starting at 0100H).

Assembler files (for Windows/DOS)

  • _ASSEMBLE.BAT - double-click in Windows to run the assembly if needed
  • TASM.EXE
  • TASM80.TAB

Acknowledgements

  • BASIC is Microsoft BASIC 4.7 for the NASCOM, heavily modified by Grant to remove references to different monitors, screen handlers and keyboard matrix reading
  • TASM assembler is a partial distribution of the package from Speech Technology Incorporated

Mechanicals

SIMPLE-Z80 REV1 MECHS.PNG

SIMPLE-Z80 Assembly Sheet