mc68181 Freescale Semiconductor, Inc, mc68181 Datasheet - Page 117

• Manufacturer Part Number: mc68181
• Description: Signal Processor
• Manufacturer: Freescale Semiconductor, Inc

Calculating How Long Tasks Take
MOTOROLA
Noise Detect
Where
Since the TimeToTaskDisabled discussed in the previous section limits how much the
host can do while the FLEXchip IC is battery saving, it is necessary for the host to
know how long it can take the FLEXchip IC to perform a task.
complete as measured from the last SPI clock of the packet that initiates the task to
the time the receiver shutdown sequence starts. Note that the receiver shutdown
sequence must start before tasks are disabled.
The following formula calculates how long it will take to complete a Noise Detect
started by setting the SND bit in the roaming control packet. This formula assumes
that (1) the noise detect was performed while in synchronous mode or (2) the noise
detect was performed in asynchronous mode and did not find FLEX signal or (3) the
noise detect found FLEX signal but the DAS bit of the roaming control packet was set.
Where
TNF
SkippedFrames
ReceiverOffTime
The formulas below calculate how long the two types of host initiated tasks take to
TotalWarmUpTime
TimeToPerformNoiseDetect
Freescale Semiconductor, Inc.
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MC68181 Technical Data Sheet
Time to Next Frame. Value from the receiver shutdown
packet.
The number of frames that will not be decoded. This can be
calculated from the Current Frame (CF) and Next Needed
Frame (NAF) fields in the receiver shutdown packet (e.g. If
CF is 10 and NAF is 12, then SkippedFrames is 1)
The time programmed in the receiver off setting packet.
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The sum of the times programmed for the used warm up
steps plus the time programmed for the 3200sps Sync
Setting in the receiver control configuration packets.
TotalWarmUpTime
Using the Receiver Shutdown Packet
+
82ms
MC68181
C-13