Hitachi H8/3937 Series Hardware Manual page 397

2. Calculating How Long Tasks Take
Since the TimeToTaskDisabled discussed in the previous section limits how much the host can do
while the FLEX decoder is battery saving, it is necessary for the host to know how long it can take
the FLEX decoder to perform a task.
The formulas below calculate how long the two types of host initiated tasks take to 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.
TimeToPerformNoiseDetect ≤ TotalWarmUpTime + 82ms
Where,
TotalWarmUpTime: The sum of the times programmed for the used warm up steps plus the
The following formula calculates how long it will take to complete an A-word search initiated by
setting the SAS bit in the roaming control packet. This formula assumes that the A-word search
failed to find roaming FLEX channel.
TimeToPerformAwordSearch ≤ TotalWarmUpTime + AST + 47ms
Where,
TotalWarmUpTime: The sum of the times programmed for the used warm up steps plus the
AST:
The following formula calculates how long it will take to complete a Noise Detect/A-word search
combination. This can occur when the noise detect is performed while in asynchronous mode, the
noise detect finds FLEX signal, and the DAS bit of the roaming control packet is not set.
TimeToPerformBoth ≤ TotalWarmUpTime + AST +127ms
Where,
time programmed for the 3200sps Sync Setting in the receiver control
configuration packets.
time programmed for the 3200sps Sync Setting in the receiver control
configuration packets.
The value configured using the timing control packet.
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