MC68HC705JJ7 Datasheet, PDF (118/164 Pages) Freescale Semiconductor, Inc – Microcontrollers

Personality EPROM (PEPROM)
12.4 PEPROM Reading
This sequence shows how to read the PEPROM:
1. Select a bit by writing to the PEBSR.
2. Read the PEDATA bit in the PESCR.
3. Store the PEDATA bit in RAM or in a register.
4. Select another bit by changing the PEBSR.
5. Continue reading and storing the PEDATA bits until the required personality EPROM data is
retrieved and stored.
Reading the PEPROM is easiest when each PEPROM column contains one byte. Selecting a row 0 bit
selects the first bit, and incrementing the PEPROM bit select register (PEBSR) selects the next bit in row
1 from the same column. Incrementing PEBSR seven more times selects the remaining bits of the column
and ends up selecting the bit in row 0 of the next column, thereby setting the row 0 flag, PEPRZF.
NOTE
A PEPROM byte that has been read can be transferred to the personality
EPROM bit select register (PEBSR) as a temporary storage location such
that subsequent reads of the PEBSR quickly yield that PEPROM byte.
12.5 PEPROM Erasing
MCUs with windowed packages permit PEPROM erasing with ultraviolet light. Erase the PEPROM by
exposing it to 15 Ws/cm² of ultraviolet light with a wavelength of 2537 angstroms. Position the ultraviolet
light source 1 inch from the window. Do not use a shortwave filter. The erased state of a PEPROM bit is
a logic 0.
MC68HC705JJ7 • MC68HC705JP7 Advance Information Data Sheet, Rev. 4.1
118
Freescale Semiconductor