NAiS FP0-A80, Technical Manual

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FP0 A/D Converter Unit 4.1 I/O Number of A/D Converter Unit
4-3 Matsushita Electric Works (Europe) AG
Conversion data switch flags
The resolution of the A/D converter unit is 12 bits, but when data is transferred to the
control unit, it is converted to 16–bit data. Therefore, although the WX2 data requires no
processing, for the WX3 data, the top two bits are used as conversion data switching
flags. Accordingly, the top two bits are processed as follows.
When the A/D conversion data is negative “–”, the WX2 and WX3 data become two’s
complement.
In other words, bit C to bit F of WX2 and bit C to bit D of WX3 become “1”.
Also, because the top two bits of WX3 are used as conversion data switch flags, masking
is required so that the bits are “00” when the conversion data is positive “+”, and “11”
when the conversion data is negative “–”.
Ch3 data WX3
→
Data after masking
1 0100000000000001
→
0000000000000001
–1 0111111111111111
→
1111111111111111
Conversion data switch flags Mask applied to the above values