M16C User Manual.pdf

A-D ConverterMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER2.7.3 Operation of A-D Converter (in one-shot mode, an external trigger selected)In one-shot mode, choose functions from those listed in Table 2.7.3. Operations of the circled items aredescribed below. Figure 2.7.7 shows timing chart, and Figure 2.7.8 shows the set-up procedure.Table 2.7.3. Choosed functionsItemSet-upItemSet-upOperation clockφADResolutionAnalog input pinOOODivided-by-4 fAD / dividedby-2fAD / fAD8-bit / 10-bitOne of AN0 pin to AN7 pinExpanded analoginput pinONot usedEither ANEX0 pin orANEX1 pinExternal operation amplifierconnection modeTrigger for startingA-D conversionOSoftware triggerTrigger by ADTRGSample & HoldONot activatedActivatedOperation___________(1) If the level of the ADTRG changes from “H” to “L” with the A-D conversion start flag set to “1”,the A-D converter begins operating.(2) After A-D conversion is completed, the content of the successive comparison register (conversionresult) is transmitted to A-D register i. At this time, the A-D conversion interrupt requestbit goes to “1”. Also the A-D converter stops operating.___________(3) If the level of the ADTRG pin changes from “H” to “L”, the A-D converter carries out conversion___________from step (1) again. If the level of the ADTRG pin changes from “H” to “L” while conversion isin progress, the A-D converter stops the A-D conversion in process, and carries out conversionfrom step (1) again.(1) Start A-D conversion (2) A-D conversion iscomplete8-bit resolution : 28 φAD cycles10-bit resolution : 33 φAD cycles(3) Start A-DconversionφADA-Dconversionstart flag“1”“0”Set to “1” by softwareADTRG“H”“L”A-D register iResultA-D conversioninterrupt request“1”“0”Cleared to “0” when interrupt request is accepted, or cleared by softwareNote: When φAD frequency is less than 1MHZ, sample and hold function cannot be selected.Conversion rate per analog input pin is 49 φAD cycles for 8-bit resolution and 59 φAD cycles for 10-bit resolution.Figure 2.7.7. Operation timing of one-shot mode, with an external trigger selected390