I have been characterizing the Intersil IS82C55AZ and have found it to be both faster and stronger than reported in the data sheet.

The Iol at Vol = 0.4v was measured at 14 mA at 5V and 25C. That implies a true spec of Iol = 8mA. The data sheet says Iol = 2.5mA.

The Ioh at Voh = Vdd - 0.4 was 10 mA. That implies a true spec of Ioh = 6mA. The data sheet says Ioh = 100uA.

The chip timing depends strongly on Vdd. At Vdd = 5V, I was seeing 40nS access times. That corresponds to a spec of 75nS. The data sheet says that access times are 120nS.

In other notes, the part worked down to about 1.5 volts, the date code was July, 2006, and the data sheet had a date of January, 2006.

From these measurements, it appears that the Intersil 82C55 would have no problem with working in the data space of the 8051 (12x clock) at almost any frequency.

And yet there have been many criticisms of the 8255 here. So, has the unhappiness with the 8255 been a result of reading the data sheet, or do they result from actual, recent experience?