Re: question about PC-AT V2

Philippe, it's not clear to me what exactly the problem is.

"VI1 does arrive at IR1 on the 8259 but INT is not asserted"

then:-

"the 8259 seems to work fine as INT is generated and INTA"

The INTA will only be generated by the 8259A if it gets and accepts an INT.

Have you tried another INT vector.

John

On Friday, June 5, 2015 at 10:37:01 AM UTC-7, Philippe Elie wrote:

Hi folks,

I finished the PC-AT V2 board and started testing it with the 8086 V1 board (running monitor 10.33). All fine, RTC and timer look OK but I have trouble when testing the BIOS keyboard functions.

I use the Propeller board so jumpered VI1 and I do see the appropriate LED on the LED bar of the PC-AT blink when I hit a key. VI1 does arrive at IR1 on the 8259 but INT is not asserted. the 8259 seems to work fine as INT is generated and INTA as well as displayed by D2 and D1 when jumping VI0 to the system tick on P54.

I checked the way the 8259 is initialized : when entering the 8086 monitor, I clear the interrupt mask with "QO21 00" and I see D2 (INT) blink to reflect VI0. then I mask VI0 (QO21 01) but still get no INT when hitting the keyboard.

the 8259 seems properly accessed as all bit patterns written to 021H are read back correctly. I have the Z80 V2 board so VI0-7 are pulled up by the board (I did not install RR9 on the PC-AT board).

I'm a bit puzzled to be honest... If you guys could provide some guidance, I would be grateful

thanks
Philippe