PS-SAU-1900E
Mar. 8
th
,1999 (Rev. 0.0)
--- CONFIDENTIAL AND PROPRIETARY ---
31
ringing) will stop immediately when the phone goes off hook. This line must be debounced due to the
fact that it briefly pulses low when ringing is started.
3.2.1.2.
Caller ID Circuit Operation.
The Caller ID circuit consists of simple 8 bit microcontroller, followed by a summing network and
amplifier, and finally a low pass filter. The microcontroller is serially connected to the MSM controller.
Serial caller identification information is transmitted to this D/A at 38.4 kbps, after the MSM enables the
CID_CTO_0 (CID ENABLE) control line. The MCU then formats the data into the appropriate CID format,
as indicated by the data header information. This serial data is then used to control the 8 bit output into
the ladder network / summing amplifier circuitry. The outputs are stepped to create a continuous phase
sine wave output, whose frequency is modulated according to the requirements of the CID standard. The
sine wave is amplified, low pass filtered, then applied to a summing point on the analog loop interface.
3.2.2.
Power Supply Module.
The power supply board has two control inputs, as shown below.
Control Signal
State
Function
DCDC_0
0 - Power Supply is OFF.
*
1 - Power Supply is ON.
-65/-24Vdc Power
Supply ON/OFF control.
DCDC_1
0 - Off Hook Loop Voltage = -24 Vdc.
1 - On Hook Loop Voltage = -65 Vdc.
Loop Voltage control.
Values in
italics
are the settings at power-up
* DCDC_0 must stay 0 till SLIC mode is initialized.
The power supply is controlled via the MSM processor, and is turned on immediately after power is
applied to the product. The operating voltage level is determined by the hook switch status, as indicated
in the above table.
3.2.3.
Battery Management Module.
The Battery Management module has two control inputs, as shown below.
Control Signal
State
Function
BATT_OFF
0 - Battery is ON.
1 - Battery is OFF.
Battery source power
control.
CHG_OFF
0 - Charger circuit is ON.
1 - Charger circuit is OFF.
Loop Voltage control.
Values in
italics
are the settings at power-up.
The battery control circuit is used to turn the battery off if the battery voltage falls below a safe operating
range while the unit is being powered by the battery.
CHG_OFF is used to turn the charging circuit on and off. The charger circuit is turned off when either of
the following events occur:
•
the unit goes from AC to battery power.
