My data logger uses CMOS 4040 ripple counters to generate the
addresses needed for 128K of external static RAM. This stores 64K of
12 bit data at a maximum rate of 10K samples per second. I used a
Dallas DS1245 RAM chip which has internal battery backup thus
eliminating the write delays with EEPROM.

I also needed to store configuration data into this RAM and the first
32 locations were used for this purpose. The hard part was to skip
these locations very quickly when the storage address wrapped around to
zero. I could not simply increment the counters 32 times as the 100uS
sampling rate would be compromised.

To overcome this I used a CMOS 4029 presettable counter. With this chip
I can set the outputs to any combination I like, with  a limit of 4
bits. Thus, when the data address wraps around I simply reset this chip and the
base address for the data becomes 20h instead of 0h.

Regards

Tony


Just when I thought I knew it all,
I learned that I didn't.