Precisely.



Or any of the other modern derivatives that support ISP. There are lots of them.


Your I/O needs could be handled with a solution as simple as a couple of sub-$1 74xx573 latches.

Should you prefer something that can be connected with less wires, a serial shift register will work as Neil suggested. There are also a variety of serially-interfaced (I²C, SPI, etc.) I/O expanders from a umber of vendors, including Maxim/Dallas.


That still seems to be the case. Last time I got EPROM-based 87C51/2 devices some years ago, I remember them being about $20, and a quick search on Digi-Key a few minutes ago found none for less than that.

So, now for a little nostalgia. The OTP versions of 87C51/2 devices are significantly cheaper than their EPROM counterparts, but why? I thought the OTP devices were based on the same technology as the EPROM versions, with the primary difference being the absence of the quartz window to let in the UV light for erasing. Is the price difference largely a result of market pressures, where demand/supply are low in the era of flash-based derivatives? I realize the EPROM versions usually come in ceramic packages, but thought this was to avoid UV-induced plastic package deterioration, and was not responsible for radical price differences.

--Sasha Jevtic