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Code and design repository for the 6809v2 SBC: To be released at VCFMW 13
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6809v2 single-board computer (c) 2018 David Wood This system is a 3.68mhz 6809-based microcomputer with 128k RAM and 8K rom. It is intended to run 6809-based operating systems that run within 64k of RAM such as FLEX or OS-9 Level I. All I/O services are provided via a 68681 DUART, either via one of its serial ports or via the extra GPIO pins on the device. This documentation is primarily a placeholder and will likely be improved as time goes on(TM). ;-) System memory map: 0000-DFFF System RAM E000-FEFF System ROM (ROMON=high) or System RAM(ROMON=low) FF00-FF0F 68681 DUART (see below for I/O definitions) FF10-FFDF reserved: Don't use FFE0-FFFF System ROM (ROMON=high) or System RAM(ROMON=low) DUART I/O Map: IP0 CTS port A IP1 CTS port B IP2 DCD port A (not routed) IP3 DCD port B (not routed) IP4 n/c IP5 SD Data input Input from Micro SD OP0 RTS port A OP1 RTS port B OP2 RAM A16 A16 to RAM OP3 RAM A17 A17 to RAM (128k has CE2 here) OP4 ROMON High enables the 2764 eprom OP5 SDCK Clock output to Micro SD OP6 SDDO Data output to Micro SD OP7 SDCS Chip select output to Micro SD NOTE: The 68681 sets all outputs high on reset NOTE: The 68681 inverts its output port bits A summary of programming-related information is also printed on the pcb. The memory fitted with a standard 128k-256k sram. A 512k device can be fitted but the board lacks sufficient hardware to bankswitch more than 256k. A jumper bridge under the SRAM will allow disconnecting A18 from ground. Directories: kicad/ Kicad v<5.0 files used to design the board sbug/ S-BUG port to the 6809v2 SBC (working) tests/ Prototype test code segments sdcard/ SD-Card code (not yet finished) ** Many thanks to Dolo@hackaday.IO for the sdcard sample code and permission for the author to use it as long as the code for the firmware remains free and open! ** License: CC:SA license v4.0 I encourage the sharing and adaptation of this design as long as some credit to me is given in the firmware and/or board design. Reach me at firstname.lastname@example.org