MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 60
Manufacturer Part Number
FREESCALE [Freescale Semiconductor, Inc]
Erasable Programmable Read-Only Memory
4.5 EPROM/OTPROM Programming
Erasable Programmable Read-Only Memory (EPROM/OTPROM)
The unprogrammed state is a 0. Programming changes the state to a 1.
Use the following procedure to program a byte of EPROM/OTPROM:
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.
Writing to an invalid address prevents the programming voltage from
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 the ELAT bit is cleared. This is to ensure
a proper programming sequence. If EPGM is set and a valid EPROM
write occurs, V
EPGM bit is cleared, the program voltage is removed from the array.
1. Apply V
2. Set the ELAT bit.
3. Write to any user EPROM/OTPROM address.
4. Set the EPGM bit.
5. Wait for a time, t
6. Clear the ELAT and EPGM bits.
for application information on how to use this pin.
to the IRQ/V
will be applied to the user EPROM array. When the
Section 14. External Interrupt