MC68HC708MP16 Datasheet, PDF (57/398 Pages) Freescale Semiconductor, Inc – Microcontrollers

EPROM/OTPROM
4.5 EPROM/OTPROM Programming Sequence
The unprogrammed state is a 0. Programming changes the state to a 1.
Use the following procedure to program a byte of EPROM/OTPROM:
1. Apply V_DD + V_HI to the IRQ1/V_PP pin.
2. Set the ELAT bit.
NOTE:
Writing logic 1s to both the ELAT and EPGM bits with a single instruction
sets only the ELAT bit. EPGM must be set by a separate instruction in
the programming sequence.
3. Write to any user EPROM/OTPROM address.
NOTE: Writing to an invalid address prevents the programming voltage from
being applied.
4. Set the EPGM bit.
5. Wait for a time, t_EPGM.
6. Clear the ELAT and EPGM bits.
Setting the ELAT bit configures the address and data buses to latch data
for programming the array. Only data written to a valid EPROM address
will be latched. Attempts to read any other valid EPROM address after
step 2 will read the latched data written in step 3. Further writes to valid
EPROM addresses after the first write (step 3) are ignored.
The EPGM bit cannot be set if ELAT bit is cleared. This is to ensure
proper programming sequence. If EPGM is set and a valid EPROM write
occurred, V_PP will be applied to the user EPROM array. When the EPGM
bit is cleared, the program voltage is removed from the array.
MC68HC708MP16 — Rev. 3.1
Freescale Semiconductor
EPROM/OTPROM
Technical Data
57