I have a question on clearing the Global Interrupt Enable (GIE) bit on the 16C77 chips. On the older 16C74 chips, when you cleared the GIE you had to loop until you were certain that the bit was cleared. This was due to a problem where if an interrupt occurred as you were clearing the GIE, your ISR would execute and re-enable the GIE on completion of the ISR. The new manual implies that this bug may have been fixed on the '77 chip. However we are experiencing a problem (very low occurrence rate and difficult to pin down) that *could* be explained by this known bug on the older '74 chip. So my question is: Did they fix this problem, or do they need to fix the new data sheet? Any help will be appreciated! Russ Steinbach Russ Steinbach Manager, Research and Analysis Dept. Analex Corporation 3001 Aerospace Parkway Cleveland, OH 44142 (216) 977-0094 (W) (216) 977-0200 (F) Steinbach@lerc.nasa.gov