The cursor on 6845 systems
The Alphatronic P2's use crt5027, P3 and P30 crt5037, i.e. TMS9927 ... does it work with them the same way? I couldn't find an example where a driver that uses these chips explicitly sets a cursor.
helwie44 mentioned that on a P3 (which uses 80 track floppies) you can insert a P2 disk (40 tracks, single sided) or P2S/P2U (40 tracks, double sided), and as long as your files are on the first side of the floppy, you can import these via the "Pseudo drive" P:
MAME lets me mount the image, but I get a BDOS error ... is this the same double stepping problem as with 360K disks in 1.2M drives on PC drivers?
The 8085's RST lines are used in the Alphatronics, 7.5 connects to the keyboard system, 6.5 is vsync ("Bildimpuls-Lücke") and 5.5 hsync ("Zeilenimpuls-Lücke"). According to helwie44 connecting these will help the P2 driver continue from its current waiting (HLT) state.
For the vsync signal, the source contains the line
MCFG_TMS9927_VSYN_CALLBACK(INPUTLINE("maincpu", I8085_RST65_LINE)) MCFG_DEVCB_XOR(1)
Is this all that's needed or is there additional code required?
Currently, the vram is setup as
AM_RANGE(0x03000, 0x03bff) AM_WRITEONLY AM_SHARE("vram")
. helwie44 says, the vram should be readable from the main cpu as well as from the display controller. Would changing to AM_RAM AM_SHARE do the trick?