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MC68HC705C8 Functional Data
3.16 OTPROM/EPROM Programming
The OTPROM or EPROM programming technique is used to load a user
program into the MC68HC705C8 MCU OTPROM or EPROM. This type
of programming is accomplished via a bootstrap mode of operation.
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3.16.1 Erasing
MC68HC705C8 EPROM MCUs are erased by exposure to a highintensity ultraviolet (UV) light with a wavelength of 2537 angstrom. The
recommended dose (UV intensity x exposure time) is 15 Ws/cm2. UV
lamps should be used without shortwave filters, and the EPROM MCU
should be positioned about one inch from the UV lamps.
MC68HC705C8 one-time programmable ROM (OTPROM) MCUs are
shipped in an erased state and are packaged in an opaque plastic
package; thus, erasing operations cannot be performed on OTPROM
MCUs.
3.16.2 Programming
Programming operations are controlled by software-accessible control
bits. The software program which programs the internal
EPROM/OTPROM is located in either the on-chip bootstrap ROM or
internal RAM.
The first programming method uses a program in the bootstrap ROM to
read information from an external 8K by 8 EPROM and to program this
information into the on-chip EPROM/OTPROM. The external EPROM is
connected to I/O port pins of the MC68HC705C8. In this programming
method, information to be programmed into the internal
EPROM/OTPROM is first programmed into the external EPROM using
an industry-standard PROM programmer.
A second programming method allows user programs developed on a
personal computer to be downloaded to the MC68HC705C8 for
programming into the on-chip EPROM/OTPROM. This method
eliminates the extra steps needed to program a separate 8K by 8
EPROM. A small program that runs on the personal computer is
M68HC05 Applications Guide — Rev. 4.0
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MC68HC705C8 Functional Data
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