U3741BM Datasheet, PDF (17/32 Pages) ATMEL Corporation – UHF ASK RECEIVER IC

U3741BM
If the receiver is set to polling mode via pin ENABLE, an ‘L’ pulse (T_Doze) must be issued
at that pin. Figure 18 illustrates the timing of that command. After the positive edge of
this pulse, the sleep time T_Sleep elapses. The receiver remains in sleep mode as long as
ENABLE is held to ‘L’. If the receiver is polled exclusively by a microcontroller, T_Sleep can
be programmed to 0 to enable a instantaneous response time. This command is the
faster option than via pin DATA at the cost of an additional connection to the
microcontroller.
Figure 17. Timing Diagram of the OFF Command Via Pin DATA
Out1 (microcontroller)
t1
t2
t3
t5
t4
t10
t7
DATA (U3741BM)
X
Serial bi-directional
X
data line
Receiver
on
Bit 1
("1")
(Start bit)
OFF command
Figure 18. Timing Diagram of the OFF Command Via Pin ENABLE
T_Doze
T_Sleep
toff
ENABLE
DATA (U3741BM)
X
Serial bi-directional
data line
X
Receiver on
T_Sleep
X
X
Startup mode
X
X
Startup mode
Configuration of the
Receiver
The U3741BM receiver is configured via two 12-bit RAM registers called OPMODE and
LIMIT. The registers can be programmed by means of the bi-directional DATA port. If
the register contents have changed due to a voltage drop, this condition is indicated by a
certain output pattern called reset marker (RM). The receiver must be reprogrammed in
that case. After a power-on reset (POR), the registers are set to default mode. If the
receiver is operated in default mode, there is no need to program the registers.
Table 3 on page 18 shows the structure of the registers. According to Table 2 on page
18, bit 1 defines if the receiver is set back to polling mode via the OFF command, (see
section “Receiving Mode” on page 15) or if it is programmed. Bit 2 represents the regis-
ter address. It selects the appropriate register to be programmed.
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