Enhanced Queued Analog-to-Digital Converter (EQADC)
MPC5644A Microcontroller Reference Manual, Rev. 6
1022
Freescale Semiconductor
The EQADC Null Message Send Format Register only affects how the
EQADC sends a null message, but it has no control on how the EQADC
detects a null message on receiving data. The EQADC detects a null
message by decoding the MESSAGE_TAG field on the receive data. Refer
to
for more information on the MESSAGE_TAG field.
NOTE
Writing to the EQADC Null Message Send Format Register while the serial
transmissions are enabled (ESSIE field configured to 0b11 in
Section 25.5.2.1, EQADC Module Configuration Register
(EQADC_MCR)
) is not recommended.
25.5.2.4
EQADC External Trigger Digital Filter Register (
EQADC
_ETDFR)
The EQADC External Trigger Digital Filter Register (EQADC_ETDFR) is used to set the minimum time
a signal must be held in a logic state on the CFIFO triggers inputs to be recognized as an edge or level
gated trigger. The Digital Filter Length field specifies the minimum number of system clocks that must be
counted by the digital filter counter to recognize a logic state change. However, there is a control signal
that can be used to bypass the digital filter when this is not needed.
Table 25-6. EQADC Null Message Send Format Register (EQADC_NMSFR) field description
Field
Description
6-31
NMF[0:25]
Null Message Format
The NMF field contains the programmable null message send value for the EQADC. The
value written to this register will be sent as a null message when serial transmissions from
the EQADC SSI are enabled (ESSIE field configured to 0b11 in
Module Configuration Register (EQADC_MCR)
) and either
• there are no triggered CFIFOs with commands bound for external CBuffers, or;
• there are triggered CFIFOs with commands bound for external CBuffers but the external
CBuffers are full.
Refer to
Section , Null Message Format for External Device Operation
, for more information
on the format of a null message.
Summary of Contents for MPC5644A
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