MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
1095
Preliminary—Subject to Change Without Notice
Figure 24-91. RSD Adder
24.6.11.2.4
Variable Gain Amplification (VGA) for Pre-gain
The VGA starts after sampling completes. It is enabled by a 2-bit signal PRE_GAIN described in
Section 24.5.3.6, “Alternate Configuration 1-8 Control Registers (ADC_ACR1-8)
.
The ADC takes 2, 8, 64 or 128 clock cycles to do sampling which is selected by the LST[0:1] field in the
conversion command message. After the sampling, if 2x VGA is enabled, there is a 2x gain stage without
comparison before the regular conversion cycles. When 4x VGA is enabled, there are the 2x gain stage
without comparison by 2 times before the normal conversion processing.
24.6.12 Supported EQADC Configurations
This section discusses supported EQADC configurations and how such configurations affect the number
of effective external signals. A complete list of the EQADC external signals can be found in
In the EQADC, CFIFO commands have three possible destinations: the on-chip ADC0, the on-chip
ADC1, and the external device which is accessible through the EQADC SSI. Considering the number of
command destinations there are five possible configurations for the EQADC, out of which only three are
supported by the current implementation - see
. EQADC configurations that do not have a
serial interface to an external device are not supported.
Table 24-37. Possible EQADC Configurations
1
Name
Description: Valid Command Destinations
Support by Current
Implementation?
2ADC_1EXT
On-chip ADC0, on-chip ADC1, and external device
Yes
1ADC_1EXT
On-chip ADC0 and external device
Yes
0ADC_1EXT
External device
Yes
2ADC_0EXT
On-chip ADC0 and on-chip ADC1
No
1ADC_0EXT
External device
No
a13
b12 a12
b11 a11
b10 ..
.. ...
... a3
b2 a2
b1
------------------------------------------
s12 s11 s10 ... ... s2 s1
carry
+