On Fri, 9 Jan 1998 17:53:10 -0600, you wrote:

>> The PIC-range processors have harvard architecture, meaning that data
>> memory is separated from program memory. You cannot read the program rom ->
>>you cannot checksum.
>
>The Analog Devices fixed point DSP chips are also Harvard architecture (or
>is it 'modified' Harvard artchitecture?), but they were clever enough to
>include a bus exchange for transferring between program and data space.
>They use a dedicated register to hold the extra byte (program memory is 24
>bits, data memory is 16 bits).
>
>I've always wondered why Microchip didn't do something similiar.
'cos it isn't necessary - *if programmed correctly*, ROM corruption
just doesn't happen, so the extra cost of a verification mechanism
isn't justified. Unfortunately, some standards have been written which
require it, and MCT added a facility to the 16C715 for this reason.
 
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