HD64F7050 RENESAS [Renesas Technology Corp], HD64F7050 Datasheet - Page 463

• Manufacturer Part Number: HD64F7050
• Description: 32-Bit RISC Microcomputer SuperH RISC engine Family/
• Manufacturer: RENESAS [Renesas Technology Corp]

Bit 6—Clock Select (CKS): Selects the A/D conversion time. A/D conversion is executed in a
maximum of 266 states when CKS is 0, and a maximum of 134 states when 1. To prevent
incorrect operation, ensure that the ADST bit in A/D control register 0 (ADCR0) is cleared to 0
before changing the A/D conversion time. For details, see section 14.4.3, Analog Input Setting and
A/D Conversion Time.
Bit 5—A/D Start (ADST): Starts or stops A/D conversion. A/D conversion is started when ADST
is set to 1, and stopped when ADST is cleared to 0.
Note that the operation of the ADST bit differs between single mode and scan mode.
In single mode and scan mode, ADST is automatically cleared to 0 when A/D conversion ends on
one channel. However, in scan mode, when all conversions have ended for the selected analog
inputs, ADST remains set to 1 in order to start A/D conversion again for all the channels.
Therefore, the ADST bit must be cleared to 0, stopping A/D conversion, before changing the
conversion time or the analog input channel selection.
Ensure that the ADST bit in ADCR0 is cleared to 0 before switching the operating mode.
Also, make sure that A/D conversion is stopped (ADST is cleared to 0) before changing A/D
interrupt enabling (bit ADIE in ADCSR0), the A/D conversion time (bit CKS in ADCR0), the
operating mode (bits ADM1 and ADM0 in ADSCR), or the analog input channel selection (bits
CH3 to CH0 in ADCSR0). The A/D data register contents will not be guaranteed if these changes
are made while the A/D converter is operating (ADST is set to 1).
Bits 4 to 0—Reserved: These bits are always read as 1, and should only be written with 1.
Bit 6:
CKS
0
1
Bit 5:
ADST
0
1
Description
Conversion time = 266 states (maximum)
Conversion time = 134 states (maximum)
Description
A/D conversion is stopped
A/D conversion is being executed
[Clearing conditions]
Single mode: Automatically cleared to 0 when A/D conversion ends
Scan mode: Cleared by writing 0 in ADST after confirming that ADF in ADCSR0
is 1
Rev. 5.00 Jan 06, 2006 page 443 of 818
Section 14 A/D Converter
REJ09B0273-0500
(Initial value)
(Initial value)