First post, by vladstamate
- Rank
- Oldbie
Hi all,
I am having some issues with the IBM PC 5162 (XT/286) BIOS in my emulator. It sets the 8253 channel 1 to mode 0 then repeatedly reads the 4th bit of port 0x61 from the 8042 (since the 286/XT comes with an 8042 and not a PPI) and waits for it to flip. According to Bochs port list
bit 4 toggles with each refresh request
I assume that means RAM refresh. The problem with mode 0 in 8253 is that it is an "interrupt on terminal count". So it gets fired once and then...no more. That means I think that there is no more RAM fresh. And no more flipping of bit 4 on status word of port 0x61 of the 8042. And...the BIOS eventually hangs with a HALT.
So, am I misunderstanding how "interrupt on terminal count" works or maybe how RAM refresh and timer channel 1 works?
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