SH7137 Datasheet, PDF (733/1160 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperH™ RISC engine Family

Section 17 A/D Converter (ADC)
When the ACE bit is 0 (initial value) and the A/D conversion result (H'0222) is not written to
ADDR for some reason, the old data (H'0111) becomes the ADDR value. In addition, when the
ADDR value is read into a general register using an A/D conversion end interrupt, the old data
(H'0111) is stored in the general register. To detect a renewal failure, every time the old data needs
to be stored in the RAM, a general register, etc.
When the ACE bit is 1, reading ADDR = H'0111 by the CPU or DTC automatically clears ADDR
to H'0000. After this, if the A/D conversion result (H'0222) cannot be transferred to ADDR for
some reason, the cleared data (H'0000) remains as the ADDR value. When this ADDR value is
read into a general register, H'0000 is stored in the general register. Just by checking whether the
read data value is H'0000 or not allows the detection of an ADDR renewal failure.
• ACE bit = 0 (Normal condition: Auto-clear function is disabled.)
A/D conversion result
A/D data register (ADDR)
H'0111
H'0222
A/D conversion end interrupt
RAM, general register etc.
Read
H'0333
ADDR renewal failure
H'0111
H'0444
H'0333
Read
H'0111
Read
H'0333
• ACE bit = 1 (Auto-clear function is enabled.)
A/D conversion result
A/D data register (ADDR)
H'0111
A/D conversion end interrupt
RAM, general register etc.
Because ADDR is not renewed, old data is used.
However, it is impossible to know that the data is old or not.
H'0222
H'0111
H'0333
H'0444
ADDR renewal failure
H'0000
H'0333 H'0000
Automatic clearing
after read
Read
H'0111
Automatic clearing
after read
Read
H'0000
Automatic clearing
after read
Read
H'0333
When H'0000 is read, a failure is detected by software.
Figure 17.7 Example of When ADDR Auto-clear Function is
Disabled (Normal Condition)/Enabled
Rev. 2.00 Sep. 10, 2008 Page 707 of 1130
REJ09B0402-0200