pk87.2

        UPGARDING A PK-87 TO A PK-88    12/02/89

      The first step is to discover which version of the PK-87 you have, the
difference lies in the crystal used in the clock oscillator. The old version
has a 2.4576MHz crystal while the newer version has a 4.9152 MHz crystal.

Items required :-     32k static RAM low power (e.g.HN62256LP-15)
                      PK-88 EPROM
PLUS for older
version of PK-87 :-   4.9152 MHz HC18/U parallel resonant crystal
                      220pF high stabilty capacitor

NOTE: There are two versions of the PK-88 to date. In the context of
  EPROM upgrades they differ in the device used for U 22 (in PK-88),
  the old version having a 74HCT4040 and the new a 74HCT4020. 
CONTINUED IN FILE PK87.11