u3745bm ATMEL Corporation, u3745bm Datasheet - Page 11

• Manufacturer Part Number: u3745bm
• Description: Receiver
• Manufacturer: ATMEL Corporation

Polling Mode
Sleep Mode
4663A–RKE–06/03
•
•
•
The clock cycle of some function blocks depends on the selected baud rate range
(BR_Range) which is defined in the OPMODE register. This clock cycle T
by the following formulas for further reference:
According to Figure 3, the receiver stays in polling mode in a continuous cycle of three
different modes. In sleep mode, the signal processing circuitry is disabled for the time
period T
all signal processing circuits are enabled and settled. In the following bit check mode,
the incoming data stream is analyzed bit by bit contra a valid transmitter signal. If no
valid signal is present, the receiver is set back to sleep mode after the period T
This period varies check by check as it is a statistical process. An average value for
T
current consumption is I
dependent on the duty cycle of the active mode and can be calculated as:
During T
tee the reception of a transmitted command, the transmitter must start the telegram with
an adequate preburst. The required length of the preburst is dependent on the polling
parameters T
(T
be tested.
The following formula indicates how to calculate the preburst length.
T
The length of period T
the extension factor XSleep, according to table 10, and the basic clock cycle T
calculated to be:
In US and European applications, the maximum value of T
is set to 1. The time resolution is about 2 ms in that case. The sleep time can be
extended to almost half a second by setting XSleep to 8. XSleep can be set to 8 by bit
XSleep
below:
XSleep
I
T
Spoll
BR_Range =
Bitcheck
Preburst
Sleep
Start,µC
USA Applications
(f
Europe Applications
(f
Other applications
(T
characteristic is given as a function of T
XTO
XTO
=
Clk
=
Std
I
----------------------------------------------------------------------------------------------------------
Std
is given in the section “Electrical Characteristics”. During T
). T
³ T
Sleep
Soff
Sleep
Sleep X
is dependent on f
= 4.90625 MHz, MODE = L, T
= 6.76438 MHz, MODE = H, T
= 1 implies the standard extension factor. The sleep time is always extended.
or by bit XSleep
Sleep
Bitcheck
´
while consuming low current of I
T
and T
Sleep
T
Sleep
´
Sleep
+ T
Sleep
BR_Range0:
BR_Range1:
BR_Range2:
BR_Range3:
, T
thus depends on the actual bit rate and the number of bits (N
+
Startup
Startup
+
Startup
I
Son
T
´
Sleep
Startup
1024
, the receiver is not sensitive to a transmitter signal. To guaran-
´
S
+ T
, T
XTO
(
= I
T
is defined by the 5-bit word Sleep of the OPMODE register,
Bitcheck
Temp
Startup
+
Bitcheck
´
Son
and on the logical state of pin MODE. The electrical
T
T
Bitcheck
Clk
. The average current consumption in polling mode is
resulting in a different mode of action as described
T
T
T
T
+
+ T
XClk
XClk
XClk
XClk
and the startup time of a connected microcontroller
T
Bitcheck
Start_ m C
Clk
= 8 ´ T
= 4 ´ T
= 2 ´ T
= 1 ´ T
Clk
= 2.0383 µs)
= 2.0697 µs)
)
Clk
S
).
Clk
Clk
Clk
Clk
= I
Soff
. During the start-up period, T
Sleep
is about 60 ms if XSleep
Startup
U3745BM
and T
XClk
Bitcheck
is defined
Bitcheck
Clk
Bitcheck
Startup
. It is
) to
the
11
,
.