Simple analog to digital converter with a variable resolution of
n bits. It converts the input voltage ppin.v-npin.v
to
an n-vector of type Logic (9-valued logic according to IEEE 1164
STD_ULOGIC). The input resistance between positive and negative pin
is determined by Rin
. Further effects (like input
capacities) have to be modeled outside the converter, since this
should be a general model.
The input signal range (VRefLo,VRefHi) is divided into 2^n-1
equally spaced stages of length Vlsb:=(VRefHi-VRefLo)/(2^n-1). The
output signal is the binary code of k
as long as the
input voltage takes values in the k-th stage, namely in the range
from Vlsb*(k-0.5)
to m*(k+0.5)
. This is
called mid-tread operation. Additionally the output can only change
its value if the trigger signal trig
of type Logic
changes to '1' (forced or weak).
The output vector is a 'little-endian'. i.e., that the first bit y[1] is the least significant one (LSB).
This is an abstract model of an ADC. Therefore, it can not cover the dynamic behaviour of the converter. Hence the output will change instantaneously when the trigger signal rises.