MC705P6ACPE Datasheet, PDF (57/98 Pages) Freescale Semiconductor, Inc – M68HC05 Microcontrollers

Chapter 10
EPROM
10.1 Introduction
The user EPROM consists of 48 bytes of user page zero EPROM from $0020 to $004F, 4608 bytes of
user EPROM from $0100 to $12FF, the two MOR reset values located at $1EFF and $1F00, and 16 bytes
of user vectors EPROM from $1FF0 to $1FFF. The bootloader ROM and vectors are located from $1F01
to $1FEF.
10.2 EPROM Erasing
NOTE
Only parts packaged in a windowed package may be erased. Others are
one-time programmable and may not be erased by UV exposure.
The MC68HC705P6A can be erased by exposure to a high-intensity ultraviolet (UV) light with a
wavelength of 2537 angstroms. The recommended dose (UV intensity multiplied by exposure time) is
15 Ws/cm². UV lamps without shortwave filters should be used, and the EPROM device should be
positioned about one inch from the UV lamp. An erased EPROM byte will read as $00.
10.3 EPROM Programming Sequence
The bootloader software goes through a complete write cycle of the EPROM including the MOR. This is
followed by a verify cycle which continually branches in a loop if an error is found. A sample routine to
program a byte of EPROM is shown in Table 10-1.
NOTE
To avoid damage to the MCU, V_DD must be applied to the MCU before V_PP.
10.4 EPROM Registers
Three registers are associated with the EPROM: the EPROM programming register (EPROG) and the
two mask option registers (MOR). The EPROG register controls the actual programming of the EPROM
bytes and the MOR. The MOR registers control the six mask options found on the ROM version of this
MCU (MC68HC05P6), the EPROM security feature, and eight additional port A interrupt options.
10.5 EPROM Programming Register (EPROG)
This register is used to program the EPROM array. Only the ELAT and EPGM bits are available.
Table 10-1 shows the location of each bit in the EPROG register and the state of these bits coming out of
reset. All the bits in the EPROG register are cleared by reset.
MC68HC705P6A Advance Information Data Sheet, Rev. 2.1
Freescale Semiconductor
57