The MC68HC705B5 is a device similar to the MC68HC05B6, but with the 6 kbytes ROM and 256 bytes EEPROM replaced by a single EPROM array. In addition, the self-check routines available on the MC68HC05B6 are replaced by bootstrap firmware. The MC68HC705B5 is intended to operate as a one time programmable (OTP) version of the MC68HC05B6 without EEPROM or the MC68HC05B4, meaning that the application program can never be erased once it has been loaded into the EPROM. The entire MC68HC05B6 data sheet applies to the MC68HC705B5, with the exceptions outlined in this appendix.

　　MC68HC705B5 Features

　　6206 bytes EPROM (including 14 bytes User vectors)

　　No EEPROM

　　Bootstrap firmware

　　Simultaneous programming of up to 4 bytes

　　Data protection for program code

　　Optional pull-down resistors on port B and port C

　　MC68HC05B6 mask options are programmable using control bits held in the options register

　　52-pin PLCC and 56-pin SDIP packages

High speed version not available

MC68HC705B5 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 VDD.

 

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