Rainbow Electronics U3741BM - Manual (Page 12)

12
U3741BM
4662B–RKE–10/04
X
SleepStd
= 1 implies the standard extension factor. The sleep time is always extended.
X
SleepTemp
= 1 implies the temporary extension factor. The extended sleep time is used
as long as every bit check is OK. If the bit check fails once, this bit is set back to 0 auto-
matically resulting in a regular sleep time. This functionality can be used to save current
in presence of a modulated disturber similar to an expected transmitter signal. The con-
nected microcontroller is rarely activated in that condition. If the disturber disappears,
the receiver switches back to regular polling and is again sensitive to appropriate trans-
mitter signals.
According to Table 7 on page 19, the highest register value of Sleep sets the receiver to
a permanent sleep condition. The receiver remains in that condition until another value
for Sleep is programmed into the OPMODE register. This function is desirable where
several devices share a single data line.
Figure 8. Polling Mode Flow Chart
Bit-check
OK?
Sleep: 5-bit word defined by Sleep0 to Sleep4 in
OPMODE register
NO
YES
Sleep Mode:
All circuits for signal processing are
disabled. Only XTO and polling logic is
enabled.
Output level on pin IC_ACTIVE => low
I
S
= I
SON
T
Sleep
= Sleep
×
X
Sleep
Ч
1024
Ч
T
Clk
Start-up Mode:
The signal processing circuits are
enabled. After the start-up time (T
Startup
) all
circuits are in stable condition and ready
to receive.
I
S
= I
SON
T
Startup
Bit-check Mode:
The incomming data stream is analyzed.
If the timing indicates a valid transmitter
signal, the receiver is set to receiving
mode. Otherwise it is set to Sleep mode.
I
S
= I
Son
T
Bit-check
Receiving Mode:
The receiver is turned on permanently
and passes the data stream to the
connected microcontroller. It can be set to
Sleep mode through an OFF command
via pin DATA or ENABLE
I
S
= I
SON
OFF command
X
Sleep
: Extension factor defined by X
SleepTemp
according to Table 8
T
Clk
: Basic clock cycle defined by f
XTO
and pin
MODE
T
Startup
: Is defined by the selected baud rate range
and T
Clk
. The baud-rate range is defined
by Baud0 and Baud1 in the OPMODE
register.
T
Bit-check
: Depends on the result of the bit check.
If the bit check is ok, T
Bit-check
depends
on the number of bits to be checked
(N
Bit-checked
) and on the utilized data rate.
If the bit check fails, the average time
period for that check depends on the
selected baud-rate range on T
Clk
. The
baud-rate range is defined by Baud0 and
Baud1 in the OPMODE register.