W925E240 Datasheet, PDF (64/73 Pages) Winbond – 8-BIT CID MICROCONTROLLER

W925E/C240
CPE goes off-hook
Start Point
CPE mutes handset & disables keypad
CPE sends
Tip/Ring
CAS
ACK
Mark
Note 1
A
B
C
D
E
F
Note 3
ASE
CIDF
ALGO
t _REC
t _ABS
CPE unmutes handset and
enable keypad
Message
G
H
...
FSKE
Note 2
Note 4
Note 5
FCD
FDR
FCLK
FDATA
...
A = 40 - 50mS
B = 80 - 85mS
C <= 100mS
D = 65 - 75mS
E = 5 - 100mS
F = 40 - 75mS
Data
G = depends on data length
H <= 100mS
Figure 7-5 Input and Output Timing of BT Loop State (Off-hook) Data Transmission
Notes:
1. In a CPE where AC power is not available, the designer may choose to switch over to line power when the CPE goes
off-hook and use battery power while on-hook.
2. The FSKE bit may be set low to prevent the alert tone, speech or other FSK in-band noise decoded by FSK
demodulator and give false data when the dual tone alert signal is expected. If the FSKE pin cannot controlled by micro-
controller, the FSKE bit must always placed in high state and the micro controller must give up the FSK decoded data
when the FSK signal is not expected.
3. The exchange will have already disabled the speech path to the distant customer in both transmission directions.
4. The FSKE should be set high as soon as the CPE has finished sending the acknowledge signal ACK.
5. The FSKE may be set low after the last byte (check sum) has been decoded or FCD has become inactive.
6. In an unsuccessful attempts where the exchange does not send the FSK signal, the CPE should disable FSKE, un-mute
the handset and enable the keypad after this interval.
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