65C816 ECB SBC

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I have had this idea rattling around in my head for a 65816 ECB SBC for some time now – and I had some free time on a family trip, so I put form to that thought. With a tremendous amount of assistance from John Coffman, I am pleased to say the the 65C816 SBC is a reality.

I will be adding more documentation to this page, as the project progresses – I hope to get firmware running on the board with support for the RBC disk controllers and Video adapters.

For now, we have a ROM monitor (based on Supermon 816– big thank you to BCS technology for making this software free to use/modify) working that supports the following commands:

A — Assemble code
C — Compare memory regions
D — Disassemble code
F — Fill memory region (cannot span banks)
G — Execute code (stops at BRK)
H — Search (hunt) memory region
J — Execute code as a subroutine (stops at BRK or RTS)
L -- Load a Motorola format S28 file into memory
M — Dump & display memory range
R — Dump & display 65C816 registers
T — Copy (transfer) memory region                                        > — Modify up to 32 bytes of memory
; — Modify 65C816 registers

I am working on building out hardware support in the BIOS. At the moment only Serial Read/Write, DISKIO V3 Floppy and On board RTC is supported.

Long Term I intend to have support in the BIOS for:

• DISKIO V3 (HDD/FDD)
• VGA3
• Dual SD
• DualDMA Disk (HDD/FDD)
• Color VDU
• VDU
• SCG

The memory map is:

000000 - 007FFF On Board RAM
008000 - 00FDFF On Board RAM or ROM - ROM can be software selectable to 32K or a choice of a 8 or 16K bank - bank size selectable in GAL equations
00FE00 - 00FE06 16550 UART
00FE07 - FE07 RTC & ROM SIZE SELECTION FLAG
00FE08 - 00FEFF Mapped to Z80 ports for ECB bus boards (IO)
00FF00 - 00FFFF BIOS and Hardware Vectors
   00FF00 - 00FF70 Native mode jump table
   00FF71 - 00FFEF Emulation Mode jump table
   00FFF0 - 00FFFF Hardware Vectors
010000 - 07FFFF On Board RAM
080000 - FFFFFF Open to ECB Bus

Current BIOS functions are:
Long Call:
FF00 LOUTCH - output char in A to serial port
FF03 LINCH - get char from serial port into A
FF08 LINCHW - get char from serial port into A (Blocking)
FF0C LINITDISK - initialize storage device (supports DISKIO V3 Floppy only at the moment)
FF10 LREADDISK - Read Disk Sector into BIOS buffer (supports DISKIO V3 Floppy only at the moment)
FF14 LWRITEDISK - write Disk Sector from BIOS buffer (supports DISKIO V3 Floppy only at the moment)
FF18 LWRITERTC - Write value to RTC register
FF1C LREADRTC - Read value from RTC register

Short Call:
FF71    OUTCH     - output char in A to serial port
FF74    INCH      - get char from serial port into A
FF77    INCHW     - get char from serial port into A (Blocking)
FF7A    INITDISK  - initialize storage device (supports DISKIO V3 Floppy only at the moment)
FF7D    READDISK  - Read Disk Sector into BIOS buffer (supports DISKIO V3 Floppy only at the moment)
FF80    WRITEDISK - write Disk Sector from BIOS buffer (supports DISKIO V3 Floppy only at the moment)
FF83    WRITERTC  - Write value to RTC register
FF86    READRTC   - Read value from RTC register

The ROM file can be built with the Western Design Centers tool set that is available for free from the WDC web site. http://wdc65xx.com/wdctools-download-2/

Note that while these tools do have a couple of bugs that require careful attention to syntax, they appear to be generally usable. Both an assembler and C compiler are available.

All of the souce files as well as an assembled binary are in the ZIP file.