CMOSTEK CMT2157A, Manual

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CMT2157A
Rev 0.8 | Page 20/31 www.cmostek.com
Address (Sync ID)
configurable 8-11 bits
Data
4-1 bit(s)
Sync
32 symbols
Figure 20. 2262 Packet Structure
Bit Format
In 2262 packet, a single bit is constructed by 8 symbols, as shown below. Please note that only the Address (Sync ID) field and
the Data
field have the unit of “bit”. In the below diagram, 1 OSC clock cycle is notated as 1 α referring to the original 2262
timing descriptions.
3 SYM
(12
α
)
1 SYM
(4
α
)
3 SYM
(12
α
)
1 SYM
(4
α
)
Bit 1
3 SYM
(12
α
)
1 SYM
(4
α
)
Bit 0
3 SYM
(12
α
)
1 SYM
(4
α
)
3 SYM
(12
α
)
1 SYM
(4
α
)
Bit f
3 SYM
(12
α
)
1 SYM
(4
α
)
Figure 21. 2262 Bit Format Options
5.8 ID Study
The ID Study function, which is supported in 1920 and 1527 modes, allows the receiver to study the Sync ID sent by the
CMT2157A. Since then, the receivers Sync ID is identical to that of the CMT2157A and therefore two devices are paired. The
lengths of the Sync ID are different in the different packet formats. In 1920 format, it is from 1 to 32 bits. In 1527 format, it is
fixed at 20 bits.
The ID Study is initialized by the CMT2157A. It is done by executing the following steps. An example of CMT2157A paring with
CMT2250/51A is given below.
1. Press the Study Button on the CMT2157A and hold it over the time defined by the “Study Trigger Time”.
2. CMT2157A starts to transmit the Study Packets, wait 1-2 seconds then release the Study Button.
3. Try to press a certain button on the CMT2157A to check if the CMT2250/51A react correctly.
The figure below shows the timing characteristic after pressing down a study button. The Study Power is always independently
configure from the TX Power. In this example, the Study Power is set smaller than the TX Power.
One Normal
Packet
Packet
Interval
Study Button
Pressed
time
Study Button
Released
Study Time
(Default is 5 s)
One Study
Packet
Packet
Interval
TX Power = 0 dBm
Study Power = -6 dBm
Figure 22. Timing of Study Button Pressing Event
More information about the ID Study can be found in the document “AN142 CMT2157A Configuration Guideline”.