Background on using HSYNC and VSYNC
in the Alphatronic P3 / P30 and P2 / P2S / P2U systems
With the TA P3 / P30
systems only those with a RIM (i8085) the signals VSYNC: = int6.5 and / or HSYNC: = int5.5 are polled. In order to make an input or output to the DISPLAY memory. No real interrupt is used for the diplay transfer. Since the VSYNC was already installed in the alphatpx.cpp, the display output started almost immediately.
The MOS in the EPROM 1000h-17FFh of the P2 series
is a bit different.
The text output (characters)
takes place via the real INT6.5
of the picture key gaps (approximately period 20ms). The output prepares the necessary parameters and puts out a HLT (i8085). Then, with a triggered int6.5, the service routine will process the character output.
But as soon as a "rollup" is triggered, this is initiated via the VSYNC via int5.5. Therefore, the first image output hung first. (wait until finally - because no int5.5 was set up by the MESS!)
Unfortunately, the mechanism available by now HSYNC is due to bad time response
of user input / etc.
I already had a patched original TA EPROM "14G" signature some time ago to change the IMASK from 0Eh (int5.5 open) to IMASK to 0Dh (int6.5 open) just one byte in the rollup area.
Here theDisplayDriver EPROM "14g"
and a pdf of the patch
hexadump with references.
All display requirements are only processed via the VSYNC, ie the int6.5. The result is very good.
Thank you for all contributions and valuable help.
The reaction speed is exactly like the P3 / P30 machine.