U3741BM Datasheet, PDF (16/25 Pages) ATMEL Corporation – UHF ASK RECEIVER IC

U3741BM
Table 10.Effect of the configuration word Lim_max
Lim_max
Lim_max < 12 is not applicable
0
0
1
1
0
0
0
1
1
0
0
0
1
1
1
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
0
1
1
0
0
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
Upper Limit Value for Bitcheck
(T_{Lim_max} = (Lim_max –1) × XLim × T_Clk)
0
12
1
13
0
14
.
.
.
0
24 (Default)
(USA: T_{Lim_max} = 375 µs, Europe: T_{Lim_max} = 381 µs)
.
.
.
1
61
0
62
1
63
Conservation of the Register Information
The U3741BM implies an integrated power-on reset and
brown–out detection circuitry to provide a mechanism to
preserve the RAM register information.
According to figure 21, a power-on reset (POR) is
generated if the supply voltage V_S drops below the
threshold voltage V_ThReset. The default parameters are
programmed into the configuration registers in that
condition. Once V_S exceeds V_ThReset the POR is canceled
after the minimum reset period t_Rst. A POR is also
generated when the supply voltage of the receiver is
turned on.
To indicate that condition, the receiver displays a reset
marker (RM) at Pin DATA after a reset. The RM is
represented by the fixed frequency f_RM at a 50% duty
cycle. RM can be canceled via an ‘L’ pulse t1 at Pin
DATA. The RM implies the following characteristics:
D f_RM is lower than the lowest feasible frequency of a
data signal. By this means, RM cannot be misinter-
preted by the connected µC.
D If the receiver is set back to polling mode via pin
DATA, RM cannot be canceled by accident if t1 is
applied according to the proposal in the section
‘Programming the configuration registers’.
By means of that mechanism the receiver cannot lose its
register information without communicating that condi-
tion via the reset marker RM.
VS
POR
DATA (U3741BM) X
V _ThReset
t _Rst
Figure 21. Generation of the power on reset
1 / f _RM
16 (25)
Preliminary Information
Rev. A1, 15-Oct-98