This application note describes the changes needed in both hardware
and software to migrate a design from the MC68HC705J2 (J2) to the
MC68HC705JJ7 (JJ7). Not only is the JJ7 less expensive than the J2,
but migrating to the JJ7 also allows the designer to utilize some of its
features not found on the J2.
The JJ7’s additional features are:
? 6160 bytes of user EPROM; J2 has 2064 bytes
? 224 bytes of low-power user RAM; J2 has 112 bytes
? 64 bits of personality EPROM, serial port accessible
? 16-bit programmable timer with input capture and output compare
? Simple serial input/output port (SIOP) with interrupt capability
? Two voltage comparators, one of which can be combined with the
16-bit programmable timer to create a 4-channel, single-slope A/D
(analog-to-digital) converter
? Output of voltage comparator can drive port pin PB4 directly under
software control
? High-source/sink current capability on six I/O (input/output) pins