A-D Converter
Mitsubishi microcomputers
M16C / 6N0 / 6N1 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
157
Note 1: Does not depend on use of sample and hold function.
Note 2: Without sample and hold function, set the AD frequency to 250kHz min.
With the sample and hold function, set the AD frequency to 1MHz min.
In either case, the AD frequency may not exceed 10 MHz.
Table 1.17.1. Performance of A-D converter
A-D Converter
The A-D converter consists of one 10-bit successive approximation A-D converter circuit with a capacitive
coupling amplifier. Pins P00 to P07, P20 to P27, P100 to P107, P95, and P96 function as the analog signal
input pins. The direction registers of these pins for A-D conversion must therefore be set to input. The VREF
connect bit (bit 5 at address 03D716) can be used to isolate the resistance ladder of the A-D converter from
the reference voltage input pin (VREF) when the A-D converter is not used. Doing so stops any current
flowing into the resistance ladder from VREF, reducing the power dissipation. When using the A-D con-
verter, start A-D conversion only after setting the VREF connect bit (bit 5 at address 03D716) to connect
VREF.
The result of A-D conversion is stored in the A-D registers of the selected pins. When set to 10-bit precision,
the low 8 bits are stored in the even addresses and the high 2 bits in the odd addresses. When set to 8-bit
precision, the low 8 bits are stored in the even addresses.
Table 1.17.1 shows the performance of the A-D converter. Figure 1.17.1 shows the block diagram of the A-
D converter, and Figures 1.17.2 and 1.17.3 show the A-D converter-related registers.
Item
Performance
Method of A-D conversion
Successive approximation (capacitive coupling amplifier)
Analog input voltage (Note 1) 0V to AVCC (VCC)
VCC = 5V, f2AD divided by 1, 2, or 4. f2AD=f(XIN)/2 (PCLK0 ="0")
f2AD=f(XIN) (PCLK0 ="1")
Operating condition AD
(Note 2)
Resolution
8-bit or 10-bit (selectable)
Absolute precision
VCC = 5
Without sample and hold function
±3LSB
With sample and hold function (8-bit resolution)
±2LSB
With sample and hold function (10-bit resolution)
AN0 to AN7, AN00 to AN07, and AN20 to AN27 input : ±3LSB
ANEX0 and ANEX1 input (including mode in which external
operation amp is connected) : ±7LSB
Operating modes
One-shot mode, repeat mode, single sweep mode, repeat sweep mode 0, and
repeat sweep mode 1
Analog input pins
24 pins (AN0 to AN7, AN00 to AN07 and AN20 to AN27) + 2 pins (ANEX0 and ANEX1)
A-D conversion start condition Software trigger
A-D conversion starts when the A-D conversion start flag changes to "1"
External trigger (can be retriggered)
A-D conversion starts when the A-D conversion start flag is "1" and the
ADTRG/P97 input changes from "H" to "L"
Conversion speed per pin Without sample and hold function
8-bit resolution: 49 AD cycles, 10-bit resolution: 59 AD cycles
With sample and hold function
8-bit resolution: 28 AD cycles, 10-bit resolution: 33 AD cycles