MC68HC05B6_13 Datasheet, PDF (167/302 Pages) Freescale Semiconductor, Inc – Microcontrollers

C.2
EPROM
The MC68HC705B5 has a total of 6206 bytes of EPROM, 256 bytes being reserved for the
EPROM1 array (see Figure C-2). The EPP bit (EPROM protect) is not operative on the EPROM1
array, making it possible to program it after the main EPROM has been programmed and
protected. The reset and interrupt vectors are located at $1FF2-$1FFF and the EPROM control
register described in Section C.3.1 is located at address $0007.
The EPROM array is supplied by the VPP6 pin in both read and programming modes. Typically
the user’s software will be loaded in a programming board where VPP6 is controlled by one of the
bootstrap loader routines (bootloader mode). It will then be placed in an application where no
programming occurs (user mode). In this case the VPP6 pin should be hardwired to V_DD.
An erased EPROM byte reads as $00.
Warning: A minimum V_DD voltage must be applied to the VPP6 pin at all times, including
power-on, as a lower voltage could damage the device. Unless otherwise stated,
EPROM programming is guaranteed at ambient (25°C) temperature only
C.2.1 EPROM programming operation
The User program can be used to program some EPROM locations, provided the proper
procedure is followed. In particular, the programming sequence must be running in RAM, as the
EPROM will not be available for code execution while the ELAT bit is set. The VPP6 switching must
occur externally, after the EPGM bit is set, for example, under the control of a signal generated on
a pin by the programming routine.
Note:
Unless the part has a window for reprogramming, only the cumulative programming of
bits to logic 1 is possible if multiple programming is made on the same byte.
To allow simultaneous programming of up to 4 bytes, they must be in the same group of addresses
which share the same most significant address bits; only the two LSBs can change.
MC68HC05B6
Rev. 4.1
MC68HC705B5
14
Freescale
C-5