root@apal.UUCP (Andreas Mueller) (03/16/91)
-- I need some information about the AUTOMATIC *DTACK GENERATION (ADG) used in the AMIGA: 1. Where (memory locations) is ADG done? 2. How 'fast' is the *DATCK signal available? (is it delayed, or is it >= *AS) ? 3. Is there any difference in ADG, between the Amiga models (A1000 vs. A2000)? ----------------------------------------------------------------------------- +----------------------------------------------------------------------------+ | Andreas Mueller (A1020:) | "Who left his footprints in my computercase?" | | Phone: +49 040 251 23 27 | "Strong typing is for weak minds!" | | Hamburg, FRG | | | UUCP: root@apal.UUCP | | +----------------------------------------------------------------------------+
daveh@cbmvax.commodore.com (Dave Haynie) (03/19/91)
In article <root.3192@apal.UUCP> root@apal.UUCP (Andreas Mueller) writes: >1. Where (memory locations) is ADG done? A500, A1000, and A2000 generate DTACK* automatically for every memory region except the chunk devoted to the CIA chips (8520s), which get VPA* instead. The A3000 doesn't automatically generate DTACK* (DSACK*) for any unused memory regions. Since the Zorro II bus always had DTACK* generated for it by the Amiga system logic in older system, automatic DTACK* is thus part of the Zorro II specification, and the A3000 generates it for all valid Zorro II locations. So, for anything you should be concerned about (eg, Zorro II expansion space), DTACK* is automatic in all Amigas. >2. How 'fast' is the *DATCK signal available? (is it delayed, or is it > >= *AS) ? In the 68000 based systems, DTACK* is based strictly on AS* for areas mapped for Zorro II expansion. On the A3000, DTACK* comes out during the S3 state of the Zorro II cycle, so that an expansion card can control or delay it (via OVR* or XRDY) without glitching it. In any case, these are implementation details; no hardware should count on when DTACK* is asserted. >3. Is there any difference in ADG, between the Amiga models (A1000 vs. A2000)? That's pretty much covered up above. >| Andreas Mueller (A1020:) | "Who left his footprints in my computercase?" | -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy "What works for me might work for you" -Jimmy Buffett