CM1481 Datasheet, PDF (19/24 Pages) ON Semiconductor – 2-Channel EMI Filter with ESD Protection for Headsets/Speakers

Functional Descriptions ......
Example
Over-Air
Transactions
Figure 11 (below) shows, in diagrammatic form, the sequence of tones for an Over-Air
Re-Configuration of the Tx Address between the controlling base station and the CM1481.
Figure 13 shows the complete range of tone sequences to be used with the CM1481. For
Over-Air transactions follow the steps illustrated in Figure 11 substituting the required
action in STEP 1 with the required request and confirmation from Figure 13. Note the use
of the Data Prefix tone “B” in the data field; all operations must conform to the HSC
Operational Rules which are described on the following pages.
STEP 1
Over-Air Re-Configuration Request (Tx Address) - from base
Rx Address Tones
PDreAfiTxA ^{FUTONNCTEIONPATROANMEETER}
New Tx Address Tones
+ Data Prefix
B4 0
B
Tone 1 Tone 2 Tone 3 Tone 4 Tone 5
STEP 2 Security Check (SEED) -
Tone 1 Tone 2 Data Tone 3 Tone 4 Tone 5
Prefix
from CM1481
Old Tx Address Tones
SEED Tones
s1, s2, s3
B 2 s1 s2 s3
STEP 3
Security Reply (KEY) - from base
Rx Address Tones
KEY Tones
k1, k2, k3
B 3 k1 k2 k3
STEP 4 Configuration Confirm - from CM1481
New Tx Address Tones
B8
Fig.11 Example Over-Air Re-Configuration Tone Transaction
Pseudo-
Random
Number
Information
The figure below shows the pseudo-random number generation in diagrammatic form.
The base unit controller's software and circuitry will require to emulate this function.
The SEED is a random 8-bit number produced by the CM1481. The SEED is loaded into
the register and shifted right by the amount of steps configured as: Pseudo Iterations.
Note the Exclusive-OR functions.
The result is the KEY.
s1/k1
7 MSB
6
s2/k2
/ Parallel "SEED" Parallel "KEY"
5
4
3
2
s3/k3
1
0 LSB
Ex-OR
Register Shifted Right 1 Step per Configured Iteration-Step
Fig.12 An 8-Stage Pseudo-Random Counter Employing Exclusive-OR Feedback
19
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