A-D Converter
171
Specifications in this manual are tentative and subject to change
Rev. E
MITSUBISHI MICROCOMPUTERS
M30245 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Repeat sweep mode 1
In repeat sweep mode 1, all pins are used for A-D conversion with emphasis on the pin or pins selected
using the A-D sweep pin select bit. Table 1.61 shows the specifications of repeat sweep mode 1.
Table 1.61. Repeat sweep mode 1 specifications
Resolution select function
8 or 10-bit mode select bit of A-D control register 1 (bit 3 at address 03D716)
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.
Sample and hold
Sample and hold is selected by setting bit 0 of the A-D control register 2 (address 03D416) to “1”. When
sample and hold is selected, the rate of conversion of each pin increases. As a result, a 28 fAD cycle is
achieved with 8-bit resolution and 33 fAD with 10-bit resolution. Sample and hold can be selected in all
modes. However, in all modes, be sure to specify before starting A-D conversion whether sample and hold
is to be used.
Power consumption reduction function
The VREF connect bit (bit 5 at addresses 03D716) can be used to isolate the resistance ladder of the A-D
converter from the reference voltage pin (VREF) when the A-D converter is not used. This stops any current
from flowing into the resistance ladder from VREF, reducing the power dissipation. When using the A-D
converter, start A-D conversion only after connecting VREF. Do not write A-D conversion start flag and
VREF connect bit to “1” at the same time.
Precautions
Write to each bit (except bit 6) of A-D control register 0, A-D control register 1, and to bit 0 of A-D control
register 2 when A-D conversion is stopped (before a trigger occurs). When the VREF connection bit is
changed from “0” to “1”, wait 1 s or longer before starting A-D conversion.
When changing A-D operation mode, select the analog input pin again.
Item
Specification
Function
All pins perform repeat sweep A-D conversion with emphasis on the pin or pins selected by
the A-D sweep pin select bit.
Example: AN0 selected: AN0
AN1
AN0
AN2
AN0
AN3 etc.
Start condition
Writing "1" to A-D conversion start flag.
Stop condition
Writing "0" to A-D conversion start flag.
Interrupt request
generation timing
None generated.
Input pin
AN0 to AN7.
Pin emphasis
AN0 (1 pin) AN0 and AN1 (2 pins), AN0 to AN2 (3 pins), AN0 to AN3 (4 pins).
A-D converter results
Read A-D register corresponding to selected pin (at any time).