
Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
1088
Freescale Semiconductor
Null Message Format for External Device Operation
Null Messages are only transferred through the serial interface to allow results and unsolicited control data,
like the status of the external CBuffers, to return when there are no more commands pending to transfer.
Null Messages are only transmitted when serial transmissions from the EQADC SSI are enabled (See
ESSIE field in
Section 25.5.2.1, EQADC Module Configuration Register (EQADC_MCR)
”), and when
one of the following conditions apply:
1. there are no triggered CFIFOs with commands bound for external CBuffers, or;
2. there are triggered CFIFOs with commands bound for external CBuffers but the external CBuffers
are full. The EQADC detected returning BUSYx fields indicating “Do not send commands”.
illustrates the null message send format. When the EQADC transfers a null message, it
directly shifts out the 26-bit data content inside the
Section 25.5.2.3, EQADC null message send format
. The register must be programmed with the null message send format of the
external device.
illustrates the null message receive format. It has the same fields found in a Result Message
with the exception that the ADC result is not used. Refer to
Section , Result Message Format for External
, for more information. The MESSAGE_TAG field must be set to the Null Message tag
(0b1000). The EQADC does not store into an RFIFO any incoming message with a Null Message tag.
Table 25-61. Command BUFFERx BUSY Status
BUSYx[0:1]
Meaning
0b00
Send available commands - CBuffer is empty
0b01
Send available commands
0b10
Send available commands
0b11
Do not send commands
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
RESERVED
CONTENTS OF EQADC_NMSFR
REGISTER
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
CONTENTS OF EQADC_NMSFR REGISTER
Figure 25-58. Null Message Send Format for External Device Operation
Summary of Contents for MPC5644A
Page 2: ...MPC5644A Microcontroller Reference Manual Rev 6 2 Freescale Semiconductor...
Page 24: ...MPC5644A Microcontroller Reference Manual Rev 6 24 Freescale Semiconductor...
Page 26: ...MPC5644A Microcontroller Reference Manual Rev 6 26 Freescale Semiconductor...
Page 52: ...Introduction MPC5644A Microcontroller Reference Manual Rev 6 52 Freescale Semiconductor...
Page 56: ...Memory Map MPC5644A Microcontroller Reference Manual Rev 6 56 Freescale Semiconductor...
Page 1228: ...Decimation Filter MPC5644A Microcontroller Reference Manual Rev 6 1228 Freescale Semiconductor...
Page 1440: ...FlexCAN Module MPC5644A Microcontroller Reference Manual Rev 6 1440 Freescale Semiconductor...