SH7055S Datasheet, PDF (652/1002 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7000 Series

17.5 Interrupt Sources and DMA Transfer Requests
The A/D converter can generate an A/D conversion end interrupt request (ADI0, ADI1, or ADI2)
upon completion of A/D conversions. The ADI interrupt can be enabled by setting the ADIE bit in
the A/D control/status register (ADCSR) to 1, or disabled by clearing the ADIE bit to 0.
The DMAC can be activated by an ADI interrupt. In this case an interrupt request is not sent to the
CPU.
When the DMAC is activated by an ADI interrupt, the ADF bit in ADCSR is automatically
cleared when data is transferred by the DMAC.
See section 10.4.2, Example of DMA Transfer between A/D Converter and On-Chip Memory
(Address Reload On), for an example of this operation.
17.6 Usage Notes
The following points should be noted when using the A/D converter.
1. Analog input voltage range
The voltage applied to analog input pins during A/D conversion should be in the range AV_SS ≤
AN_n ≤ AV_ref.
2. Relation between, AV_SS, AV_CC, and V_SS, V_CC
When using the A/D converter, set AV_CC = 5.0 V ±0.5 V, and AV_SS = V_SS. When the A/D
converter is not used, set AV_SS = V_SS , and do not leave the AV_CC pin open.
3. AV_ref input range
Set AV_ref = 4.5 V to AV_CC when the A/D converter is used, and AV_ref ≤ AV_CC when not used.
If conditions above are not met, the reliability of the device may be adversely affected.
4. Notes on board design
In board design, digital circuitry and analog circuitry should be as mutually isolated as
possible, and layout in which digital circuit signal lines and analog circuit signal lines cross or
are in close proximity should be avoided as far as possible. Failure to do so may result in
incorrect operation of the analog circuitry due to inductance, adversely affecting A/D
conversion values.
Also, digital circuitry must be isolated from the analog input signals (ANn), analog reference
voltage (AV_ref), and analog power supply (AV_CC) by the analog ground (AV_SS). AV_SS should be
connected at one point to a stable digital ground (V_SS) on the board.
5. Notes on noise countermeasures
A protection circuit connected to prevent damage due to an abnormal voltage such as an
excessive surge at the analog input pins (ANn) and analog reference voltage (AV_ref) should be
connected between AV_CC and AV_SS as shown in figure 17.9.
Rev.2.0, 07/03, page 614 of 960