QADC64E Enhanced Mode Operation
MPC561/MPC563 Reference Manual, Rev. 1.2
14-36
Freescale Semiconductor
14.3.10.1 Analog Subsystem
This section describes the QADC64E analog subsystem, which includes the front-end analog multiplexer
and analog-to-digital converter.
14.3.11 Analog-to-Digital Converter Operation
The analog subsystem consists of the path from the input signals to the A/D converter block. Signals from
the queue control logic are fed to the multiplexer and state machine. The end of convert (EOC) signal and
the successive-approximation register (SAR) are the result of the conversion.
shows a block
diagram of the QADC64E analog subsystem.
Figure 14-20. QADC64E Analog Subsystem Block Diagram
14.3.11.1 Conversion Cycle Times
Total conversion time is made up of initial sample time, final sample time, and resolution time. Initial
sample time refers to the time during which the selected input channel is coupled through the buffer
amplifier to the sample capacitor. This buffer is used to quickly reproduce its input signal on the sample
capacitor and minimize charge sharing errors. During the final sampling period the amplifier is bypassed,
and the multiplexer input charges the sample capacitor array directly for improved accuracy. During the
resolution period, the voltage in the sample capacitor is converted to a digital value and stored in the SAR.
Initial sample time is fixed at two QCLK cycles. Final sample time can be two or eight QCLK cycles,
depending on the value of the IST field in the CCW. Resolution time is ten QCLK cycles.
STOP
State Mach, SAR and SAR Buffer
AN44
AN59
+
-
Final
Sample
Buffer
CHAN
Decoder
+
-
COMP.
2
V
RH
V
RL
CDAC
(4 BIT)
RDAC
(7 BIT)
CONV.
CRH
CRL
4 (one is offset)
7
CCW Buffer
Data Bus
10
Result
IST
REF
WCCW EOS/EOC
Standard Converter Interface
CLK
Zero
7
Buffer
AMP
BIAS
CAP Array
Equals CDAC
Sample
.
.
.
ALTREF
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...