Hello Dwayne.

>Eg.  Read the sequence number from 8 records and find the most recent
record.
>
>00 01 02 03 04 05 06 07  (easy)
>F9 FA FB FC FD FE FF 00  (harder)
>FE FF 00 01 02 03 04 05  (harder)
>
>The problem is dealing with the wrap from FF to 00.


You can solve the problem by searching for negative difference between
consecutive records sequence numbers. 7 bit signed value should be used for
difference. The trick is that 0 - 255 = +1 in this case, i.e. transition
from 255 to 0 is treated as usual ascending of numbers.

For example, scanning records
1) 00 01 02 03 04 05 06 07 will give differences +1 and -7 (0 - 7 = -7, so 7
is more recent)
2) 08 01 02 03 04 05 06 07 "    "    "    "    "    " (1 - 8 = -7. 8 -
recent)
3) F8 F9 FA FB FC FD FE FF "    "    "    "    "    " (F8 - FF = -7. FF -
recent)
4) 00 F9 FA FB FC FD FE FF "    "    "    "    "    " (F9 - 0 = -7. 0 -
recent)
5) 00 01 02 03 04 05 06 FF "    "    "    "    "    " (FF - 6 = -7. 6 -
recent)

This method will work for 7 and 6 records too.


Regards.
_

Nikolai Golovchenko, Electrical Engineering Student
National Mining University of Ukraine www.nmuu.dp.ua
Dnepropetrovsk, Ukraine
E-mail: golovchenko@mail.ru