System information
Analog Input
VSBC-6 Reference Manual Reference – 41
A
NALOG
C
ONTROL
R
EGISTER
ACR (WRITE) 00E4h (or 01E4h via CMOS Setup)
D7 D6 D5 D4 D3 D2 D1 D0
PD1 PD0 ACQMOD RNG BIP A2 A1 A0
Table 18: Analog Control Register Bit Assignments
Bit Mnemonic Description
D7, D6 PD1, PD0 Clock and Power-Down Selection — These bits select the power savings
mode and clock source for the A/D circuit.
PD1 PD0 Mode
0 0 Normal Operation / External Clock Mode
0 1 Normal Operation / Internal Clock Mode
1 0 Standby Power-Down (STBYPD)
1 1 Full Power-Down (FULLPD)
Note! STBYPD and FULLPD selections do not affect the clock mode.
D5 ACQMOD Acquisition Mode — This bit selects the type of acquisition mode.
ACQMOD = 0 Internal Acquisition. A write to the ACR register will initiate
an acquisition interval whose duration is internally timed. Conversion starts
when this six-clock-cycle acquisition interval (3.26µs) ends.
ACQMOD = 1 External Acquisition. Use this mode for precise control of the
sampling aperture and/or independent control of acquisition and conversion
times. The acquisition and start-of-conversion is controlled with two separate
writes to the ACR register. The first write, written with ACQMOD = 1, starts
and acquisition interval of indeterminate length. The second write, written with
ACQMOD = 0, terminates acquisition and starts conversion. However, if the
second write contains ACQMOD = 1, an indefinite acquisition interval is
restarted.
Note! The address bits for the input mux (A0–A2) must have the same values on the
first and second write pulses. Power-down mode bits (PD0, PD1) can assume new
values on the second write.
D4, D3 RNG, BIP Range and Polarity Selection — These bits select the input range and
polarity on a channel-by-channel basis.
RNG BIP Input Range
0 0 0 to +5V
1 0 0 to +10V
0 1 ±5V
1 1 ±10V
Warning! The board can be damaged if voltages in excess of ±16V are applied.
D2-D0 A2, A1, A0 Input Channel Address — These bits select which input channel you wish to
convert.
A2 A1 A0 Channel
0 0 0 Channel 0
0 0 1 Channel 1
0 1 0 Channel 2
0 1 1 Channel 3
1 0 0 Channel 4
1 0 1 Channel 5
1 1 0 Channel 6
1 1 1 Channel 7