Enhanced Queued Analog-to-Digital Converter (eQADC)MPC5566 Microcontroller Reference Manual, Rev. 219-96 Freescale Semiconductor19.4.6.2 External MultiplexingThe eQADC can use from one to four external multiplexers to expand the number of analog signals thatmay be converted. Using this configuration, up to 25 additional channels can be created.• The first external multiplexer requires one common analog pin and three address pins, so althougheight additional ADC channels are created, four existing channels are lost, so there is a net additionof four channels.• For subsequent external multiplexers, only one additional internal channel is lost so there is a netaddition of seven channels.The externally multiplexed channels are automatically selected by the CHANNEL_NUMBER field of acommand message, in the same way done with internally multiplexed channels. The software selects theexternal multiplexed mode by setting the ADC0/1_EMUX bit in either ADC0_CR or ADC1_CRdepending on which ADC performs the conversion. Figure 19-52 shows the channel number assignmentsfor the multiplexed mode. Only one ADC can have its ADC0/1_EMUX bit asserted at a time.Table 19-52. Multiplexed Channel Assignments 11 The two on-chip ADCs can access the same analog input pins but simultaneous conversions are not allowed. Also, whenone ADC is performing a differential conversion on a pair of pins, the other ADC must not access either of these two pinsas single-ended channels.Input Pins Channel Number inCHANNEL_NUMBER FieldAnalogPin Name Other Functions Conversion Type Binary DecimalAN[0]–AN[7] Single-ended 0000_0000–0000_0111 0–7Used for digital address lines of the external mux 0000_1000–0000_1011 8–11AN[12]–AN[39] Single-ended 0000_1100–0010_0111 12–39VRH Single-ended 0010_1000 40VRL Single-ended 0010_1001 41(VRH – VRL ) ÷ 2 Single-ended 0010_1010 4275% x (V RH – VRL ) Single-ended 0010_1011 4325% x (V RH – VRL ) Single-ended 0010_1100 44Reserved 0010_1101–0011_1111 45–63ANWANXANYANZ————Single-endedSingle-endedSingle-endedSingle-ended0100_0xxx0100_1xxx0101_0xxx0101_1xxx64–7172–7980–8788–95DAN0+ and DAN0-DAN1+ and DAN1-DAN2+ and DAN2-DAN3+ and DAN3-DifferentialDifferentialDifferentialDifferential0110_00000110_00010110_00100110_001196979899Reserved 0011_0100–1111_1111 100–255
