Resolution Select Function; Sample And Hold; Current Consumption Reducing Function; Analog Input Pin And External Sensor Equivalent Circuit Example - Renesas M16C/29 Series Hardware Manual

M16C/29 Group

15.2 Resolution Select Function

The BITS bit in the ADCON1 register determines the resolution. When the BITS bit is set to "1" (10-bit
precision), the A/D conversion result is stored into bits 0 to 9 in the ADi register (i=0 to 7). When the BITS
bit is set to "0" (8-bit precision), the A/D conversion result is stored into bits 0 to 7 in the ADi register.

15.3 Sample and Hold

When the SMP bit in the ADCON 2 register is set to "1" (with the sample and hold function), A/D conver-
sion rate per pin increases to 28 φAD cycles for 8-bit resolution or 33 φAD cycles for 10-bit resolution. The
sample and hold function is available in one-shot mode, repeat mode, single sweep mode, repeat sweep
mode 0 and repeat sweep mode 1. In these modes, start A/D conversion after selecting whether the
sample and hold circuit is to be used or not.
Set the SMP bit to "1" (with sample and hold) in simultaneous sample sweep mode, delayed trigger mode
0 and delayed trigger mode 1.

15.4 Current Consumption Reducing Function

When the A/D converter is not used, the VCUT bit in the ADCON1 register isolates the resistor ladder of
the A/D converter from the reference voltage input pin (V
off any current flow into the resistor ladder from the V
When using the A/D converter, set the VCUT bit to "1" (V
ADCON0 register to "1" (A/D conversion started). Do not set the ADST bit and VCUT bit to "1" simulta-
neously, nor set the VCUT bit to "0" (V

15.5 Analog Input Pin and External Sensor Equivalent Circuit Example

Figure 15.5.1 shows an example of the analog input pin and external sensor equivalent circuit.
Sensor equivalent
circuit
V
IN
Figure 15.5.1 Analog Input Pin and External Sensor Equivalent Circuit
Rev.1.00 Nov 01,2004
REJ09B0101-0100Z
REF
Microcomputer
R
0
R (7.8kΩ)
C (1.5pF)
page 245 of 402
). Power consumption is reduced by shutting
REF
pin.
REF
connected) before setting the ADST bit in the
REF
unconnected) during A/D conversion.
Sampling time
Sample-and-hold function enabled :
V
C
Sample-and-hold function disabled :
15. A/D Converter
3
f
AD
2
f
AD