M16C User Manual.pdf

A-D ConverterMitsubishi microcomputersM16C / 62 GroupSINGLE-CHIP 16-BIT CMOS MICROCOMPUTER2.7.5 Operation of A-D Converter (in one-shot mode, external op-amp connection mode selected)In one-shot mode, choose functions from those listed in Table 2.7.5. Operations of the circled items aredescribed below. Figure 2.7.11 shows timing chart, and Figure 2.7.12 shows the set-up procedure.Table 2.7.5. 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) Setting the A-D conversion start flag to “1” causes voltage input to the ANi pin to be outputfrom the ANEX0 pin. The A-D conversion is carried out on voltage input to the ANEX1 pin(connect an operation amplifier between the ANEX0 pin and the ANEX1 pin).(2) After the A-D conversion is completed, the content of the successive comparison register(conversion result) is transmitted to A-D register i corresponding to the ANi pin. At this time,the A-D conversion interrupt request bit goes to “1”.Example of wiringExample of operation(1) Start A-D conversion (2) A-D conversion is completeInput voltageMicrocomputerAN0φAD8-bit resolution : 28 φAD cycles10-bit resolution : 33 φAD cycles Set to “1” by softwareInput voltageAN1A-D conversionstart flag“1”“0”Op-ampA-D register iResultANEX0ANEX1A-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 for10-bit resolution.Figure 2.7.11. Operation timing of one-shot mode, with external op-amp connection mode selected394