Vamiga: Bit BPLCON0::ERSY is ignored

[dirkwhoffmann]

ERSY: „External resync (HSYNC, VSYNC pads become inputs) (reset on power up)“ [HRM]

When ERSY equals 1, the vpos and hpos counters (the ones that are returned by VHPOSR) are no longer incremented. As a result, two consecutive reads from VHPOSR return the same result. This is not implemented yet.

„The Jetsons“ is a test case for this. While booting, it calls the following Kickstart routine which reads VHPOSR two times in a row.

In vAmiga, $102 is returned which is wrong. In UAE, 0 is returned because the ERSY bit is taken care of.

[tonioni]

KS uses ERSY=1 to detect if genlock is connected. If counters keep running with ERSY=1: genlock connected. If counters stop: no genlock. I think this slightly affects how KS uses CIA timers.