Threshold Bank And Comparator - NXP Semiconductors MPC5644A Reference Manual

Reaction Module (REACM)
Modulation
HDOFFPT
Control
The Modulation Control Word generates the address for the Hold-off Timer bank which then generates the
hold-off value for the channels. The channel that addressed the Modulation Word captures the 12-bit value
storing it in the channel Hold-off timer. In
Modulation Word thus receiving the hold-off value from the Hold-off Timer Bank. Each reaction channel
has its own internal hold-off timer.
23.4.5

Threshold bank and comparator

The Threshold bank and comparator contains the threshold levels to be compared against the ADC results.
This submodule also performs the comparison between the ADC result and the selected threshold value.
The Threshold bank can be programmed with up to 64 threshold values depending on the configuration
defined during the module integration.
An ADC result received from the on-chip ADC is connected to the ADC router and then to the comparator.
See Figure 23-23. This result stays at the comparator input until the Reaction Channel and Modulation
Control Word selects the address of the Threshold value. The THRESPT field in the Modulation Control
Word submodule is used as the address for the Threshold Bank. Note that if Threshold/Threshold
modulation mode is used two comparisons need to be executed with two different Threshold values. After
the first comparison is made the THRESPT pointer is incremented and a new comparison is done:
First comparison: COMP = ADC_DATA  THRESHOLD_VALUE[THRESPT]
•
• Second comparison: COMP = ADC_DATA < THRESHOLD_VALUE[THRESPT + 1]
The COMP (comparison result) is routed to the channel selected by the received TAG. Once having
received the comparison result the channel takes the appropriate actions in order to execute the modulation
mode as defined by the modulation control word.
722
CPU
HOLD-OFF
TIMER
4
BANK
Hold-off timer
16
Figure 23-22. Hold-off timer bank block diagram
Figure 23-22
MPC5644A Microcontroller Reference Manual, Rev. 6
Hold-off time value[11:0]
(to all Reaction channels)
12
hdt hdt
CH0 CH1
channel CH0 is requesting access to the
Reaction Channels
hdt
CHn
Freescale Semiconductor