U3742bm – Rainbow Electronics U3742BM User Manual
Page 23
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U3742BM
4735A–RKE–11/03
Figure 24. Timing of the Register Programming
Programming the
Configuration Register
The configuration registers are programmed serially via the bi-directional data line
according to Figure 24 and Figure 25.
Figure 25. One-wire Connection to a Microcontroller
To start programming, the serial data line DATA is pulled to 'L' for the time period t
1
by
the microcontroller. When DATA has been released, the receiver becomes the master
device. When the programming delay period t
2
has elapsed, it emits 14 subsequent syn-
chronization pulses with the pulse length t
3
. After each of these pulses, a programming
window occurs. The delay until the program window starts is determined by t
4
, the dura-
tion is defined by t
5
. Within the programming window, the individual bits are set. If the
microcontroller pulls down pin DATA for the time period t
7
during t
5
, the bit is set to '0'. If
no programming pulse t
7
is issued, this bit is set to '1'. All 14 bits are subsequently pro-
grammed in this way. The time frame to program a bit is defined by t
6
.
Bit 14 is followed by the equivalent time window t
9
. During this window, the equivalent
acknowledge pulse t
8
(E_Ack) occurs if the just programmed mode word is equivalent to
the mode word that was already stored in that register. E_Ack should be used to verify
that the mode word was correctly transferred to the register. The register must be pro-
grammed twice in that case.
Programming of a register is possible both during sleep and active mode of the receiver.
Out1
(microcontroller)
DATA (U3742BM)
Serial bi-directional
data line
X
Bit 1
("0")
Bit 2
("1")
Bit 13
("0")
Bit 14
("1")
X
t
1
t
2
t
3
t
4
t
5
t
6
t
8
t
7
T
Sleep
Programming frame
(Startbit)
(Register-
select)
(Poll8)
(Poll8R)
Receiving
mode
Startup
mode
t
9
Internal pull-up
resistor
Bi-directional
data line
DATA
I/O
U3742BM
Microcontroller
Data
(U3742BM)
Out 1 (microcontroller)