Probably 74F573, bipolar "fast" TTL logic. Anyway, the CMOS "A" parts, like 74AHC573, are very close in speed to the old "F" chips. Jan-Erik. Tal wrote: > What you mean F parts? -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu