CMX641AD2 View Datasheet(PDF) - CML Microsystems Plc
Part Name
Description
MFG CO.
'CMX641AD2' PDF : 26 Pages View PDF
Dual SPM/Security Detector/Generator
CMX641A
Figure 5 Tone Follower and Packet Mode Outputs
1.6.4 Setting Level Sensitivity via the Input Serial Data Word
The serial data word input is used to set the device sensitivity in the Controlled Sensitivity mode of the
Fixed Bandwidth Operating state and in the Enhanced Features Operating state.
In Controlled Sensitivity mode of the Fixed Bandwidth Operating state, the CMX641A operates identically
to the FX641 and MX641. The input word is 6 bits and Table 2 lists the device sensitivities vs input
codes.
In the Enhanced Features Operating State, channel 1’s sensitivity is controlled by applying the codes in
Table 2 to bits D15-D11. Channel 2’s sensitivity is controlled by applying these codes to bits D8-D4.
Example: Suppose the CMX641A is required to work in a system in which 16kHz signals, at or above
–22dB(ref) must be detected and signals at or below –27dB(ref) must not be detected. Reference to
Table 2 shows that bandpass filter gain settings of 6dB or 7dB will meet this level specification.
Thus in Fixed Bandwidth Operating State and Controlled Sensitivity Mode:
Inputting D5-D0 = ’001100’ or ‘001110’ (See Table 2) will set both channels to meet this specification.
Selecting ‘001100’ makes both channels’ minimum ‘Will Detect’ level –22.9dB(ref) and its maximum ‘Will
Not Detect’ level –25.5dB(ref). This means that the detection threshold of any device will lie between
these two levels.
In Enhanced Features Operating State Channel 2:
Inputting D15-D11 = ‘00110’ or ‘00111’ (See Tables 2 & 3) and D1-D0 = ‘00’ (See Table 6) will
programme channel 2 to meet this level specification. Selecting ‘00111’ makes the channel 2 minimum
‘Will Detect’ level –23.9dB(ref) and its maximum ‘Will Not Detect’ level –26.5dB(ref). This means that
Channel 2’s detection threshold will lie between these two levels.
In Enhanced Features Operating State Channel 1:
Inputting D8-D4 = ‘00110’ or ‘00111’ (See Tables 2 & 3) and D1-D0 = ‘00’, ‘01’ or ‘10’ (See Table 6) will
programme channel 1 to meet this level specification. Selecting ‘00110’ makes the CMX641A minimum
‘Will Detect’ level –22.9dB(ref) and its maximum ‘Will Not Detect’ level –25.5dB(ref). This means that
channel 1’s detection threshold will lie between these two levels. The two channels may be set to
identical detection thresholds, if desired.
© 2002 Consumer Microcircuits Limited
16
D/641A/5
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