sbc6502a1

Single Board Computer with 65C02, clone of Apple I

Features

• Clone of Apple I.
  • similar but much ** greater ** projects are there.
    • RC6502 and RC6502 Apple 1 SBC
    • Apple 1 Mini
    • L-Star
• Communicate with Host-PC via Serial.
  • using Arduino Nano as PIA Communicator
• 32KB user RAM is available.
• ROM has 2 bank of each 8KB + 8KB.
  • it is enough for wozmon, Apple1-BASIC, OSI-BASIC and so on.
• Power supply +5VDC from Type-C or via Arduino Nano.

PCB

Schematics and Layout

BOM

Ref	Name	Qty	Description	Package	Link
U1	W65C02S	1	MPU 6502	DIP40	akizuki, mouser
U2	W65C21S	1	PIA 6521	DIP40	mouser
U3	74HC04	1		DIP14	akizuki
U4	74HC00	1		DIP14	akizuki
U5	74HC138	1		DIP16	akizuki
U6	62256	1	SRAM 32Kx8	DIP28	mouser AS6C62256-55PCN, uPD43256AC-12L-13P
U7	27C512	1	ROM 64Kx8	DIP28	W27C512-45(EEPROM), mouser AT27C512R-45PU(OTP-EPROM)
U8	MCP23S17	1	SPI/GPIO	DIP28/300mil	akizuki
A1	Arduino Nano	1	PIA Communicator		akizuki, other clones
X1	1.0 MHz	1	Crystal OSC	DIP8	akizuki 1MHz
C1	0.01uF-0.1uF	1
C2, C4, C5, C6, C7, C8, C9, C10, C11	0.1uF	9
C3	470uF	1
D1	1N4148	1		DO35
J1	2x20 Pin Header	1	Bus export
J2	USB Type-C Power	1	Power Supply		akizuki
J3	1x6 Pin Header	1	for Serial comm
JP1, JP2	1x2 Pin Header	1	jumper select
R1, R2, R3, R4	10K-100K	4	for pullup
RN1	10Kx8	1	for pullup
SW1	Push Button	1	Reset SW
SW2	Slide Switch	1	Power SW		akizuki
TP1,TP2	Test Pin	2

Note: Clock Frequency

• Original Apple1 works at 1.0 MHz
• This PCB works fine at 1.0 - 10.0 MHz
  • These clocks have been TESTED with a1basic, OSI-BASIC etc.
  • Using faster RAM and ROM, It may work even at 14 MHz, which is the limit of MPU and PIA.

Memory Map

System

Address	Size	Name	Note
0x0000 - 0x7FFF	32KB	RAM
0x8000 - 0x87FF	2KB	(N.C.)	/CS80
0x8800 - 0x8FFF	2KB	(N.C.)	/CS88
0x9000 - 0x97FF	2KB	(N.C.)	/CS90
0x9800 - 0x9FFF	2KB	(N.C.)	/CS98
0xA000 - 0xBFFF	8KB	ROM	mapped from 0x2000 or 0xA000
0xC000 - 0xC7FF	2KB	(N.C.)	/CSc0
0xC800 - 0xCFFF	2KB	(N.C.)	/CSc8
0xD000 - 0xD7FF	2KB	PIA	assigned to 0xD010
0xD800 - 0xDFFF	2KB	(N.C.)	/CSd8
0xE000 - 0xFFFF	8KB	ROM	mapped from 0x6000 or 0xE000

ROM (27C512 64KB)

Address	Bank	Note
0x0000 - 0x1FFF	Bank0 (JP1 open)	no use
0x2000 - 0x3FFF		8KB, mapped to 0xA000
0x4000 - 0x5FFF		no use
0x6000 - 0x7FFF		8KB, mapped to 0xE000
0x8000 - 0x9FFF	Bank1 (JP1 close)	no use
0xA000 - 0xBFFF		8KB, mapped to 0xA000
0xC000 - 0xDFFF		no use
0xE000 - 0xFFFF		8KB, mapped to 0xE000

License

• MIT
  • only for PCB
  • firmwares are NOT included.

Author

• [email protected]