MPC563XM Reference Manual, Rev. 1
1078
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
24.6.7.2
External Multiplexing
The EQADC can use from one to four external multiplexer chips to expand the number of analog signals
that may be converted. Up to 32 analog channels can be converted through external multiplexer selection.
The externally multiplexed channels are automatically selected by the CHANNEL_NUMBER field of a
Command Message, in the same way done with internally multiplexed channels. The software selects the
external multiplexed mode by setting the ADC0/1_EMUX bit in either ADC0_CR or ADC1_CR
depending on which ADC will perform the conversion.
shows the channel number
assignments for the multiplexed mode. There are 4 differential pairs, 39 single-ended, and, at most, 32
externally multiplexed channels which can be selected. Only one ADC can have its ADC0/1_EMUX bit
asserted at a time.
shows the maximum configuration of four external multiplexer chips connected to the
EQADC. The external multiplexer chip selects one of eight analog inputs and connects it to a single analog
output, which is fed to a specific input of the EQADC. The EQADC provides three multiplexed address
signals, MA0, MA1, and MA2, to select one of eight inputs. These three multiplexed address signals are
connected to all four external multiplexer chips. The analog output of the four multiplex chips are each
connected to four separate EQADC inputs, ANW, ANX, ANY, and ANZ. The MA pins correspond to the
three least significant bits of the channel number that selects ANW, ANX, ANY, and ANZ with MA0 being
the most significant bit - See
.
INA_ADC1_6
LVI33
Single-ended
ADC1
1100_0101
197
INA_ADC1_7
LVI50 50%
Single-ended
ADC1
1100_0110
198
INA_ADC1_8
VDDEH1A 50%
Single-ended
ADC1
1100_0111
199
Reserved
1100_1000 to
1111_1111
200 to 255
1
The two on-chip ADCs can access the same analog input pins but simultaneous conversions are not allowed.
Also, when one ADC is performing a differential conversion on a pair of pins, the other ADC must not access
either of these two pins as single-ended channels.
2
Old version has reserved values for channel numbers 8 to 11 when EMUX =1. Therefore, now the behavior is
different because it is converted the signal at AN8 to AN11, respectively.
3
VREF=VRH-VRL.
Table 24-33. Encoding of MA Pins
1
Channel Number selecting ANW, ANX, ANY, ANZ
(decimal)
MA0
MA1
MA2
ANW
ANX
ANY
ANZ
64
72
80
88
0
0
0
65
73
81
89
0
0
1
66
74
82
90
0
1
0
67
75
83
91
0
1
1
68
76
84
92
1
0
0
Table 24-32. Multiplexed Channel Assignments
1
(continued)
Input Pins
ADC
Channel Number in
CHANNEL_NUMBER Field