Raspberry Pi Tube Client (PiTubeClient)

A project to turn a Raspberry Pi into a SPI Connected Second Processor for the Acorn MMC Micro Model B or Master 128.

See:http://stardot.org.uk/forums/viewtopic.php?f=3&t=10421

Build in Commands

Command	Description
*HELP ARM	Displays the current version and list of commands
*GO	Executes code at the given address in user mode
*MEM	Displays memory in hex and ascii
*DIS	Disassembles memory
*FILL	Fills a block of memory
*CRC	Calculates the "Atom" CRC over a block of memory
*TEST	Does nothing of significance

Current Memory Map

From	To	Size	Description
00000000	0000003F	64B	ARM vectors
00008000	00008EFF	~4KB	Basic workspace
00008F00	001FFFFF	~2MB	Basic program storage
00200000	01F2FFFF	~29MB	Unused
01F30000	01F3FFFF	64KB	Undefined Instruction Stack
01F40000	01F4FFFF	64KB	Abort Stack
01F50000	01F5FFFF	64KB	User Stack
01F60000	01F6FFFF	64KB	IRQ Stack
01F70000	01F7FFFF	64KB	Supervisor Stack
01F80000	01FFFFFF	512KB	Tube Client OS
02000000	0FFFFFFF	224MB	Unused

Notes:

• PAGE = 00008F00
• HIMEM = 00200000

Memory Layout Changes to Consider

Relocate BASIC above HIMEM.

Currently the BASIC 135 executable loads to 0xF000, which is in the middle of the program area, and will cause problems for large programs.

The only reason for this is that MMFS seems to ignore the higher order bits of the address, and we are currently just using *RUN.

In fact, in DFS there are only two higher order bits, so the max load address is not significantly larger anyway.

Eventually BASIC should be a relocateable module. Until then, it might be worth writing a small boot loader.

Note: *LOAD BAS135 00200000 does work.

Move the Tube Client OS and stacks further up.

Putting them at just below 32MB was completely arbitrary.

Move HIMEM further up.

Again, placing HIMEM at 2MB was completely arbitrary.

TODO List

• Implement the SWI X flag to have errors returned in a Error Block
• SWI OS_Exit should accept params in R0,R1 and R2
• SWI's OS_IntOn and OS_IntOff currently broken
• Run time debug level settings
• Commands to enable/disable the Caches
• Port JGH's Module Handling: http://mdfs.net/User/JGH/Develop/ARMCoPro/Modules/
• Address possinle IRQ Stack Memory Leak
• Provide an option for soft vs hard reset. Possibly this could be configured on the "boot command line"
• Vectors - currently we don't implement any vectors. Then implement OS_Claim and OS_Release.
• Implement more SWIs, especially
  • OS_SynchroniseCodeAreas (SWI &6E) (called by BASIC)
  • OS_Mouse
  • OS_Byte 82-84 (read memory limits)
  • OS_ReadEscapeState
  • OS_ExitAndDie
  • OS_ReadMemMapInfo
  • OS_ValidateAddress
  • OS_LeaveOS
  • OS_ReadLine32
  • The set that Sprow implements is a good target: http://www.sprow.co.uk/bbc/hardware/armcopro/armtubeoscalls.pdf