vspicer@ccu.umanitoba.ca (05/24/91)
Hello world I'm trying to interface a home-made data acquisition board designed for an ST into a TT. I've made an adapter board which maps the VME pinouts to their ST expansion bus equivalents so the existing board just plugs in. The problem is that when I attempt to access the VME mapped memory area (FE000000 base address) I get a bus error, 2 bombs. A logic analyser reveals the AS* line on the VME bus isn't being set. I'm presuming that when I try to access VME memory space: 1- The address in question appears on the VME address lines. 2- AS* changes to low to indicate the address is valid. 3- An identity comparitor on my board sees that *AS, compares the address against a set bit pattern and engages the rest of the board if they match. The board DOES work on our ST machine, so the board isn't at fault. Shouldn't AS* change state when addressing VME memory space? Or is there more to it than that? thanks in advance vic spicer .