Module Objective Learn the difference between EPROM and OTPROM. Learn how to program the EPROM.
EPROM MODULE EPROM- Erasable, 36 Kbytes ProgrammableOTPROM
- One-Time, 36 Kbytes Programmable ROM
- MCU without the quartz window can’t be erased
EPROM/OTPROM Memory Locations:
EPROM/OTPROM Control Register EPROM Control Register (EPMCR)- EPROM/OTPROM Charge Pump Disable (EPMCPD)
- EPROM/OTPROM Latch Control (ELAT)
- Latches the address and data buses for programming
- Clearing ELAT also clears the program control bit(EPGM)
- Data cannot be read when ELAT is set
- EPROM/OTPROM Program Control (EPGM)
- Applies IRQ1/VPP voltage to EPROM/OTPROM
- ELAT must already be set to write to EPGM
EPROM/OTPROM Programming Sequence Sequence for programming a byte of EPROM/OTPROM:- 1) Apply the programming voltage to IRQ1/VPP pin 2) Set the ELAT bit
- 3) Write to any 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, tEPGM . 6) Clear the ELAT and EPGM bits
- note - Clearing the ELAT bit automatically clears the EPGM
- Setting the ELAT and EPGM bit with one instruction will set ELAT but clear EPGM.
- EPGM must be set by a separate instruction in the programming sequemce.
Security Mask Option Register (MOR)- EPROM/OTPROM Security bit (SEC)
- Prevents reading of the EPROM/OTPROM
- Writing to the MOR register has no effect
Low Power - Charge pump returns to VDD
Exiting STOP mode- Charge pump resumes/stabilizes during oscillator start up
Summary
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