> I must be getting to be a real pain at this stage, Dave, and thanks for > taking me through this.
No problem. > > A minor point but a number of microprocessors don't go to 0x0000 hex > > at reset. Reset vectors in some cases are in the 0xFF00 hex page and > > I believe the Motorola 68xx and the Hitachi 63xx are among those. > > Come to think of it, I believe that x86 reset goes to 0xFFFF00 hex to > > get it's first instruction after a reset. > > 1. Output a start signal on a presettable address (from the > address bus). Often this would be 0x0000h > 2. Given this start signal, output a stop on a clock count. > 3. Alternatively, stop on another address. > 4. Probably an optional reset signal just after the stop would > be nice to get another sample. Saves farting with a watchdog, and works > when there isn't such a device on the board. > > All of this is probably do-able from 1 Eprom clip on the board for > boards with an eprom. After that, it gets messy here due to the range of > uPs I meet (80xx, 8088, 8085, Z80, TMS7000, PICs, ATMELs, HD64xxxx, > 68xx, & 65xx being the common ones) Of the micros listed, the only ones that I know go to 0x0000 hex on reset are the 8085 and the Z80. 8031/51 and HD64180 too. The 68xx and the 65xx don't necessarily ever go to 0x0000 hex as far as I know. HP used to make a scope that used a pair of 8-bit DACs, one for the horizontal and one for the vertical, to display address patterns on the screen. I think the DAC's were loaded on the memory control signals RD and/or WR so the display wasn't just a bunch of fuzz. This works pretty good if you have a known good unit to compare the unit under test to. -=-=-=-=-=-=- "http://www.psyber.com/~dibsed"; -=-=-=-=-=-=- DIBs Electronic Design | Dave Baldwin: [EMAIL PROTECTED] Adapt and overcome. | Buy a book and read it. -=-=--=-=--=-=--=-=--=-=-=-=--=-=--=-=--=-=--=-=--=-=--=-=- -- Author: Dave Baldwin INET: [EMAIL PROTECTED] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
