MPC564EVB Freescale Semiconductor, MPC564EVB Datasheet - Page 580

• Manufacturer Part Number: MPC564EVB
• Description: KIT EVAL FOR MPC561/562/563/564
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC564EVB

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC56x
• Data Bus Width: 32 bit
• Interface Type: RS-232, Ethernet
• For Use With/related Products: MPC561, 562, 563, 564
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

QADC64E Enhanced Mode Operation
Resolution begins with the most significant bit (MSB) and works down to the least significant bit (LSB).
The switching sequence is controlled by the comparator and successive-approximation register (SAR)
logic.
14.3.15 Comparator
The comparator is used during the approximation process to sense whether the digitally selected
arrangement of the DAC array produces a voltage level higher or lower than the sampled input. The
comparator output feeds into the SAR which accumulates the A/D conversion result sequentially,
beginning with the MSB.
14.3.16 Bias
The bias circuit is controlled by the STOP signal to power-up and power-down all the analog circuits.
14.3.17 Successive Approximation Register
The input of the successive approximation register (SAR) is connected to the comparator output. The SAR
sequentially receives the conversion value one bit at a time, starting with the MSB. After accumulating the
10 bits of the conversion result, the SAR data is transferred to the appropriate result location, where it may
be read from the IMB3 by user software.
14.3.18 State Machine
The state machine receives the QCLK, RST, STOP, IST, CHAN[6:0], and START CONV signals, from
which it generates all timing to perform an A/D conversion. The start conversion signal (START CONV)
indicates to the A/D converter that the desired channel has been sent to the multiplexor. IST indicates the
desired sample time. The end of conversion (EOC) signal notifies the queue control logic that a result is
available for storage in the result RAM.
14.4
The digital control subsystem includes the control logic to sequence the conversion activity, the clock and
periodic/interval timer, control and status registers, the conversion command word table RAM, and the
result word table RAM.
The central element for control of the QADC64E conversions is the 64-entry CCW table. Each CCW
specifies the conversion of one input channel. Depending on the application, one or two queues can be
established in the CCW table. A queue is a scan sequence of one or more input channels. By using a pause
mechanism, sub queues can be created in the two queues. Each queue can be operated using one of several
different scan modes. The scan modes for queue 1 and queue 2 are programmed in QACR1 and QACR2
(control registers 1 and 2). Once a queue has been started by a trigger event (any of the ways to cause the
QADC64E to begin executing the CCWs in a queue or sub-queue), the QADC64E performs a sequence
of conversions and places the results in the result word table.
14-38
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Sample Capacitor — The sample capacitor is employed to sample and hold the voltage to be
converted.
Digital Subsystem
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor