On Thu, Jun 11, 2009 at 23:30, Carl-Daniel Hailfingerc-d.hailfinger.devel.2006@gmx.net wrote:
Ah, the common trap of MByte vs. Mbit. The chips are 4 Mbit (512 kByte), so there won't be any overlap.
No, I'm well aware of the distinction (embedded hardware designer) you are right though, I misread the datasheet (Saw M assumed Mb because it was a ROM, looking at it again they say M byte (presumably because a lot of people don't realise the difference between Mb and MB), teach me for posting to mailing lists at 22:00 ;oD )
Besides that, the Winbond datasheets explicitly mention that ID3 is not used by the chips unless I'm totally misreading them.
From my datasheet (Revision A2, dated 19/12/2002);
...For accessing the 4M byte BIOS storage space, the ID[2:0] pins are inverted in the ROM and are compared to address lines [21:19]. ID[3] can be used as like active low chip-select pin.
Ergo, tie ID3 high, chip effectively disabled, same outcome as using the ID2 pin as you say though.