Datasheet

Section 18 A/D Converter

Page 1088 of 1408 R01UH0309EJ0500 Rev. 5.00

Sep 24, 2012

H8S/2456, H8S/2456R, H8S/2454 Group

18.7 Usage Notes

18.7.1 Module Stop Function Setting

Operation of the A/D converter can be disabled or enabled using the module stop control register.

The initial setting is for operation of the A/D converter to be halted. Register access is enabled by

clearing the module stop state. Set the CKS1 and CKS2 bits to 1 to set ADCLK to φ, and clear the

ADST, TRGS1, TRGS0, and EXTRGS bits all to 0 to disable A/D conversion when entering

module stop state after operation of the A/D converter. After that, set the module stop control

Modes.

18.7.2 A/D Input Hold Function in Software Standby Mode

When this LSI enters software standby mode with A/D conversion enabled, the analog inputs are

retained, and the analog power supply current is equal to as during A/D conversion. If the analog

power supply current needs to be reduced in software standby mode, set the CKS1 and CKS2 bits

to 1 to set ADCLK to φ, and clear the ADST, TRGS1, TRGS0, and EXTRGS bits all to 0 to

disable A/D conversion. After that, enter software standby mode after executing a dummy read by

one word.

18.7.3 Restarting the A/D Converter

When the ADST bit has been cleared to 0, A/D converter stops in synchronization with the

ADCLK and then enters the standby sate. After the ADST bit has been cleared, the converter may

not actually make the transition to the standby state for up to 10 cycles (φ), so do not change the

channels of the ADCLK, motion mode, or analog input at this time.

When restarting the A/D converter right after the ADST bit has been cleared to 0, read the 16

bytes from ADDRA to ADDRH and then start the A/D converter by setting the ADST bit to 1. If

the converter is in single mode or one-cycle scan mode, however, the ADST bit can be set to 1 by

clearing the ADF bit to 0 after confirming that the ADF bit had been set to 1 on completion of the

previous round of conversion.