32. 12-Bit A/D Converter (S12AD)
Under development Preliminary document
Specifications in this document are tentative and subject to change.
32.3.3.3
Channel Selection and Self-Diagnosis (Channel-Dedicated Sample-and-Hold
Circuits not Used)
When channels and self-diagnosis are selected, A/D conversion is first performed for the reference voltage VREFH0 (×0,
×1/2, or ×1) supplied to the 12-bit A/D converter, and then A/D conversion is performed on the analog input of the
selected channels, which sequence is repeated as below.
In continuous scan mode, temperature sensor output A/D conversion select bit (TSS) and internal reference voltage A/D
conversion select bit (OCS) in ADEXICR should both be set to 0 (non-selection).
(1) A/D conversion for self-diagnosis is first started when the ADST bit in ADCSR is set to 1 (A/D conversion start) by
software, synchronous trigger (MTU or ELC), or asynchronous trigger input.
(2) When A/D conversion for self-diagnosis is completed, the A/D conversion result is stored into the A/D self-
diagnosis data register (ADRD). A/D conversion is then performed for ANn channels selected by the ADANSA
register, starting from the channel with the smallest number n.
(3) Each time A/D conversion of a single channel is completed, the A/D conversion result is stored into the
corresponding A/D data register (ADDRy).
(4) When A/D conversion of all the selected channels is completed, an S12ADI0 interrupt request is generated if the
ADIE bit in ADCSR is 1 (S12ADI0 interrupt upon scanning completion enabled). At the same time, the 12-bit A/D
converter starts A/D conversion for self-diagnosis and then starts A/D conversion on ANn channels selected by the
ADANSA register, starting from the channel with the smallest number n.
(5) The ADST bit is not automatically cleared to 0 and steps 2 to 4 are repeated as long as the bit remains 1. When the
ADST bit is set to 0 (A/D conversion stop), A/D conversion stops and the 12-bit A/D converter enters a wait state.
(6) When the ADST bit is later set to 1 (A/D conversion start), the A/D conversion for self-diagnosis is started again.
Figure 32.12
Example of Operation in Continuous Scan Mode (Basic Operation + Self-Diagnosis)
ADST
A/D conversion
started
VREFH0
(×0, ×, ×1) Waitingfor conversion
Channel 1 (AN001)
Waiting for conversion
Channel 2 (AN002)
Waiting for conversion
ADRD
ADDR1
ADDR2
A/D conversion for
self-diagnosis1
Set
(1)
Stored
A/D conversion 1
Waiting for conversion
A/Dconversion3*1
Cleared
(6)
Waiting for conversion
A/D conversion 2
Result of A/D conversion for self-diagnosis 1
Waiting for conversion
A/D conversion result 2
A/D conversion time
Self-diagnosis and scanning performed repeatedly
(2)
(3)
Set
(5)
A/D conversion for
self-diagnosis 2
A/D conversion for
self-diagnosis 3
Result of A/D conversion for self-diagnosis 2
(3)
Note: Data for A/D conversion 3 is ignored.
Interrupt generated
A/D conversion result 1
(4)
(2)
S12ADI0
Stored