NXP Semiconductors MPC5644A, Reference Manual, Page: 1076 / 1735

Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
1076 Freescale Semiconductor
A Command Message is the predefined format at which command data is stored on the CQueues. A
Command message has 32 bits and is composed of two parts: a CFIFO header and an ADC Command.
The size of the CFIFO header is fixed to 6 bits, and it works as inputs to the
FIFO Control Unit . It controls
when a CQueue ends, when it pauses, if commands are sent to internal or external buffers, and if it can
abort a serial data transmission. Information contained in the CFIFO header, together with the upper bit of
the ADC Command is used by the
FIFO Control Unit to arbitrate which triggered CFIFO will transfer the
next command. ADC commands are encoded inside the least significant 26 bits of the command message.
A Result message is composed of an RFIFO header and an ADC Result. The FIFO Control Unit decodes
the information contained in the RFIFO header to determine the RFIFO to which the ADC result should
be sent. An ADC result is always 16 bits long.
25.6.2.3.1 Message Formats for On-Chip ADC Operation
This section describes the Command/Result message formats used for on-chip ADC operation.
NOTE
Although this subsection describes how the command and result messages
are formatted to communicate with the on-chip ADCs, nothing prevents the
programmer from using a different format when communicating with an
external device through the serial interface. Refer to
Section 25.6.2.3.2,
Message Formats for External Device Operation . Apart from the BN bit, the
ADC Command of a command message can be formatted to communicate
to an arbitrary external device provided that the device returns an RFIFO
header in the format expected by the EQADC. When the FIFO Control Unit
receives return data message, it decodes the message tag field and stores the
16-bit data into the corresponding RFIFO.
Conversion Command Format for the Standard Configuration
Figure 25-50 describes the format for conversion commands when interfacing with the on-chip ADCs in
the standard configuration. The standard configuration is selected when the lowest byte (bits 24-31) of the
conversion command is set to zero. In the standard configuration, the conversion result is always routed
to one of the RFIFOs. A time stamp information can be optionally requested.
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
EOQ
PAU
SE
REP
RESERVE
D
EB
(0b0)
BN CAL MESSAGE_TAG LST TSR FMT
CFIFO Header ADC Command
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
CHANNEL_NUMBER 0 0 0 0 0 0 0 0
ADC Command
Figure 25-50. Conversion Command Format for the Standard Configuration