Datasheet

Section 19 A/D Converter
Rev. 1.50 Sep. 18, 2007 Page 446 of 584
REJ09B0240-0150
19.3 Register Descriptions
The A/D converter has the following registers.
• A/D data register A (ADDRA)
• A/D data register B (ADDRB)
• A/D data register C (ADDRC)
• A/D data register D (ADDRD)
• A/D control/status register (ADCSR)
• A/D control register (ADCR)
19.3.1 A/D Data Registers A to D (ADDRA to ADDRD)
There are four 16-bit read-only ADDR registers; ADDRA to ADDRD, used to store the results of
A/D conversion. The ADDR registers, which store a conversion result for each analog input
channel, are shown in table 19.2.
The converted 10-bit data is stored in bits 15 to 6. The lower 6 bits are always read as 0.
The data bus width between the CPU and the A/D converter is 8 bits. The upper byte can be read
directly from the CPU, however the lower byte should be read via a temporary register. The
temporary register contents are transferred from the ADDR when the upper byte data is read.
Therefore byte access to ADDR should be done by reading the upper byte first then the lower one.
Word access is also possible. ADDR is initialized to H'0000.
Table 19.2 Analog Input Channels and Corresponding ADDR Registers
Analog Input Channel
CH3 = 0 CH3 = 1
Group 0
(CH2 = 0)
Group 1
(CH2 = 1)
Group 2
(CH2 = 0)
Group 3
(CH2 = 1)
A/D Data Register to Store
Results of A/D Conversion
AN0 AN4 AN8 AN12 ADDRA
AN1 AN5 AN9 AN13 ADDRB
AN2 AN6 AN10 AN14 ADDRC
AN3 AN7 AN11 AN15 ADDRD