MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 19-57
Result Message Format for External Device Operation
Data is returned from the ADCs in the form of result messages. 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
and sends the contents of the ADC result to the appropriate RFIFO. Only data stored on the
ADC_RESULT field is stored in the RFIFOs/result queues. The ADC result of any received message with
a null data message tag will be ignored. The format of a result message returned from the external device
is shown in Figure 19-32. It is 26 bits long, and is composed of a MESSAGE_TAG field, information
about the status of the buffers (BUSY fields), and result data. The BUSY fields are needed to inform the
eQADC about when it is appropriate to transfer commands to the external command buffers.
6 BN Refer to Section , “ Conversion Command Message Format for On-Chip ADC
Operation.”
7–31 OFF_CHIP_
COMMAND
[0:24]
OFF-CHIP COMMAND Field. The OFF_CHIP_COMMAND field can be anything
decodable by the external device. It is 25 bits long and it is transferred together with
the BN bit to the external device when the CFIFO is triggered. Refer to Section ,
“ Conversion Command Message Format for On-Chip ADC Operation,” for a
description of the command message used when interfacing with the on-chip ADCs.
0123456789101112131415
Reserved MESSAGE_TAG BUSY1 BUSY0
RFIFO Header
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
ADC_RESULT
ADC Result
Figure 19-32. Result Message Format for External Device Operation
Table 19-41. Result Message Format for External Device Operation
Bits Name Description
6–7 — Reserved.
8–11 MESSAGE_TAG
[0:3]
MESSAGE_TAG Field. Refer to Section , “ Conversion Command Message Format for
On-Chip ADC Operation.”
Table 19-40. On-Chip ADC Field Descriptions: External Device Operation (Continued)
Bits Name Description
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