ITX-65C816

Features

• W65C816 CPU
  • 3.3V
  • Running at 8.33 MHz
  • Native mode (65C816 extended code) and emulation mode (65C02 code)
  • Native mode allows for 24-bit address space
• Installs into FPGA-ITX-01 backplane

CPU Internal Block Diagram

CPU Features

CPU Pinout

NOP Generator

• Validate connections between CPU and FPGA
  • Address line count up
  • Data lines send out NOP ($EA) opcode controlled by RWB and CPU Clock
  • Control lines
    • Clock to CPU (from clock divider)
    • RWB from CPU
  • Bus control lines
• VHDL code

  -- CPU signals
  IO_CPU_DATA <= x"EA" when i_CPU_RWB = '1' else
    (others => 'Z');

  CPUClkGen : entity work.counter
    generic map (n => 20)
    port map (	
      clock	=> w_cpuClk,
      clear	=> '0',
      count	=> '1',
      Q		=> w_CPUClkCount
    );

  process (i_clk_50)
    begin
      if rising_edge(i_clk_50) then
        o_CPU_PHI2 <= w_CPUClkCount(4);
      end if;
    end process;
	
  o_CPU_RESB_n <= i_n_reset;
	
  o_CPU_IRQB_n	<= '1';
  o_CPU_NMIB_n	<= '1';
  o_CPU_ABORTB	<= '1';
  o_CPU_BE			<= '1';

• Used scope and observed Address lines count up
• SignalTap capture of address lines at 0xFFFF to 0x0000 transition

Upper address bits latch

Timing

Connectors

Schematics

Pin List

U8 PIN	EP4CE15/55	5CEFA2	10C1006	FUNCTION		U8 PIN	EP4CE15/55	5CEFA2	10C1006	FUNCTION
1	GND	GND	GND	GND		2	GND	GND	GND	GND
3	3.3V	3.3V	3.3V	3.3V		4	3.3V	3.3V	3.3V	3.3V
5	GND	GND	GND	GND		6	GND	GND	GND	GND
7	PIN_AA13	PIN_AA14	PIN_R9	CPU_VPB		8	PIN_AB13	PIN_AA13	PIN_T9	CPU_RESB*
9	PIN_AA14	PIN_AA15	PIN_R10	CPU_RDY		10	PIN_AB14	PIN_AB15	PIN_T10	CPU_VDA
11	PIN_AA15	PIN_Y15	PIN_R11	CPU_ABORT		12	PIN_AB15	PIN_Y14	PIN_T11	CPU_MX
13	PIN_AA16	PIN_AB18	PIN_R12	CPU_IRQB		14	PIN_AB16	PIN_AB17	PIN_T12	CPU_PHI2
15	PIN_AA17	PIN_Y17	PIN_N9	CPU_MLB		16	PIN_AB17	PIN_Y16	PIN_M9	CPU_BE
17	PIN_AA18	PIN_AA18	PIN_M10	CPU_NMIB		18	PIN_AB18	PIN_AA17	PIN_P9	CPU_E
19	PIN_AA19	PIN_AA20	PIN_P11	CPU_VPA		20	PIN_AB19	PIN_AA19	PIN_N11	CPU_RWB
21	PIN_AA20	PIN_Y20	PIN_R13	CPU_A0		22	PIN_AB20	PIN_Y19	PIN_T13	CPU_D0
23	PIN_Y22	PIN_AB21	PIN_T15	CPU_A1		24	PIN_Y21	PIN_AB20	PIN_T14	CPU_D1
25	PIN_W22	PIN_AA22	PIN_N12	CPU_A2		26	PIN_W21	PIN_AB22	PIN_M11	CPU_D2
27	PIN_V22	PIN_W22	PIN_R14	CPU_A3		28	PIN_V21	PIN_Y22	PIN_N13	CPU_D3
29	PIN_U22	PIN_Y21	PIN_N14	CPU_A4		30	PIN_U21	PIN_W21	PIN_P14	CPU_D4
31	PIN_R22	PIN_U22	PIN_P16	CPU_A5		32	PIN_R21	PIN_V21	PIN_R16	CPU_D5
33	PIN_P22	PIN_V20	PIN_N16	CPU_A6		34	PIN_P21	PIN_W19	PIN_N15	CPU_D6
35	PIN_N22	PIN_U21	PIN_M16	N/C		36	PIN_N21	PIN_U20	PIN_M15	N/C
37	PIN_M22	PIN_R22	PIN_L16	CPU_A7		38	PIN_M21	PIN_T22	PIN_L15	CPU_D7
39	PIN_L22	PIN_P22	PIN_P15	CPU_A8		40	PIN_L21	PIN_R21	PIN_M12	CPU_A15
41	PIN_K22	PIN_T20	PIN_L14	CPU_A9		42	PIN_K21	PIN_T19	PIN_L13	CPU_A14
43	PIN_J22	PIN_P16	PIN_K16	CPU_A10		44	PIN_J21	PIN_P17	PIN_K15	CPU_A13
45	PIN_H22	PIN_N20	PIN_K12	CPU_A11		46	PIN_H21	PIN_N21	PIN_J12	CPU_A12
47	N/C	N/C	N/C	N/C		48	N/C	N/C	N/C	N/C
49	N/C	N/C	N/C	N/C		50	N/C	N/C	N/C	N/C

MultiComp Build

• GitHub repo
  • 24-bit address (upper 8-bits latched in FPGA)
  • 8.33 MHz operation
  • Tested/Working
    • Running OSI 6502
    • Microsoft 8K BASIC "in ROM"
  • VGA output
  • 1MB SRAM
  • PS/2 Keyboard

Resources

• Datasheet on Archive.org site
• The 6502/65C02/65C816 Instruction Set Decoded
• Programming the 65816
• Text version of the datasheet
• A 65816 Primer
• A 6502 Programmer's Introduction to the 65816
• INVESTIGATING 65C816 INTERRUPTS

Mechanicals

Assembly Sheet

• ITX-65C816 Rev 1 Assembly Sheet