=== Creating a minimal boot disc ===
Minimal requirements are:
* 64KB ram
* system format
* CPM+ boot sector
* C10CPM3.EMS
Using CPM2.2:
* Use disckit3 to format and install the boot sector onto the disc.
* Use PIP to copy C10CPM3.EMS to your disc (B:=A:C10CPM3.EMS)
* Your minima minimal CP/M+ disc is bootable. === Terminal font === <gallery caption="CP/M 3.0 terminal font">Image:Cpmplus.png</gallery> === Console Input === Console input (via BDOS functions) uses firmware functions and returns firmware key codes when a key is pressed. i.e. &f0 is cursor up. === Console Output/Terminal emulation === Console output is processed via the terminal emulation. Console output doesn't execute firmware control codes. A simplified VT52 terminal is emulated. Home means the top-left position. The following are supported: ESC 0 - disable status line ESC 1 - enable status line ESC 2 - set language ESC 3 - set screen mode ESC A - cursor up ESC B - cursor down ESC C - cursor left ESC D - cursor right ESC E - clear screen and move cursor to home ESC H - move cursor to home ESC I - reverse line feed ESC J - erase to end of screen ESC K - erase to end of line ESC L - insert line ESC M - delete current ESC N - delete character and move characters up ESC Y - set cursor position ESC d - erase all above ESC b - set foreground ESC c - set background (and border) ESC e - enable cursor ESC f - disable cursor ESC j - save cursor pos ESC k - restore cursor pos ESC l - erase and above cursor ESC o - erase current line ESC p - invert on ESC q - invert off ESC r - select bright (recognised but not implemented) ESC u - cancel bright (recognised but not implemented) ESC v - wrap on ESC w - wrap off ESC x - mono mode ESC y - mono c080 mode PCW and Spectrum support viewports. This is not supported on CPC. CPC assumes a single viewport covering the entire screen and it is moved up/down using software when using insert line or delete current, but moved up using hardware otherwise. ==== ESC 2 - set language ==== ESC 2 <language> <language> is 0 based. The value is anded with 7. Internally this will transfer language specific character graphics into the font for display. ==== ESC 3 - set display mode ==== Set the display mode: ESC 3 <mode number> <mode number> is 0 based. The value is anded with 3. e.g. to set mode 0: ESC,3,0 ==== ESC b - set foreground ==== Set the foreground (pen 1) colour: ESC b <colour> Colour is 0 based with 32 added. It is a 2 bits per pixel %00rrggbb colour. ==== ESC c - set background ==== Set the background (pen 0 and border) colour: ESC c <colour> Colour is 0 based with 32 added. It is a 2 bits per pixel %00rrggbb colour. ==== ESC Y - set cursor position ==== Set the cursor position: ESC Y <y> <x> Coordinates are relative to top-left and are 0 based with 32 added. e.g. for x,y of 2,10: ESC,'Y',10+32,2+32
=== Memory layout ===
* 1st 64KB has Amstrad's XBIOS (callable using 'userf'), CCP, BDOS, BIOS, screen and firmware. Screen is at &4000-&7fff. Firmware is used. AMSDOS is not used.
* ## &c1/&c2 are used, so that there is common code at &c000-&ffff. This common code has a small BDOS and BIOS. Most of the functions use trampoline code to transition to bank 0 and call into the XBIOS.
* 2nd 64KB has the TPA and the shared code.
a) ## Page C4 has WBOOT and BDOS jump + &100-&3f00 of the TPA. This calls to functions in Page c7.b) ## Page C5 has &4000-&7fff of the TPA.c) ## Page C6 has &8000-&bfff of the TPA.d) ## Page C7 has &c000-&f2fb of the TPA. From &f2fc to &ffff is the trampoline code which transitions * to 1st bank of 64KB. === Extra memory === CPM+ on the CPC uses 128KB of memory. Therefore selections C4,C5,C6,C7 must be avoided if you have additional memory. Due to the design of DkTronic's compatible RAM expansions all memory accesses to additional RAM must occur from bank 0 (i.e. 'C1') and be transferred to the TPA in bank 1 (i.e. 'C2'). Therefore access to the additional RAM follows a pattern such as this:* From running CPM program in bank 1 you need to go via code in C000-FFFF to transition to bank 0. This can be done using 'userf'.* Within bank 0, your extra memory access code must lie within the regions 0000-3FFF or 8000-BFFF. 4000-7FFF is where the paging will take place so is out of bounds. C000-FFFF is where the memory trampoline code is paged in and out so using this area is much harder.* Remember the current memory configuration (e.g. C1,C3,C0) * In bank 0 set the memory selection (e.g. 'CC') then perform your read from the extra RAM into a temporary buffer within one of the safe areas. For write you copy from a safe area into the extra memory.* Then you need to restore the memory configuration (e.g. C1,C3,C0) and trampoline back to the TPA. Therefore extra memory access on the CPC is not as fast as it could be compared to running under AMSDOS.
=== Implementing a storage device driver ===
Using "drvtable" gets the list of DPH addresses for each drive. This is actually fixed at FE2F and is referenced by the XBIOS.
Amstrad have extended implemented the extended DPH (these appear before in the Digital Research sample BIOS. The ten bytes before a DPH)give the addresses of read/write functions: * -10,-9 - address of a DD WRITE SECTOR (XBIOS) compatible sector write function* -8,-7 - address of a DD READ SECTOR (XBIOS) compatible sector read function* -6,-5 - unknown address of drive select function, but does call DD LOGIN (XBIOS) if successful* -4,-3 - unknown function, seems to be address of drive init, calls RETfunction (never called)* -2,- physical drive number (for B: this is 0 on a single-drive system and 1 on a two-drive system)* -1 - unknown usedrive type
The XBIOS calls these and assumes bank 0 is active. If you write a driver in TPA space you will need to transition to and from bank 1 using selbnk etc.
The parameters for the read / write functions are at 0BEF0h:
DB @adrv ;Selected logical drive
DB @rdrv ;Selected physical drive (from the byte at DPH-2)
DW @trk ;Track passed to SETTRK.
DW @sect ;Sector passed to SETSEC.
DW @dma ;DMA address passed to SETDMA.
DB @cnt ;Multiple I/O count passed to MULTIO
DB @dbnk ;DMA bank passed to SETBNK
=== PALETTE.COM ===
PALETTE is a COM program written by Locomotive Software and allows the colours to be changed.
The syntax is:
PALETTE <background> <foreground>
<background> and <foreground> are r,g,b colour codes with 2 bits for each colour defined in binary as r1 r0 g1 g0 b1 b0. Therefore black is 000000, bright white is 111111, white (grey) is 010101 and bright red is 110000.
=== Links ===