TELEFUNKEN Semiconductors

U3810BM

Rev. A1: 19.01.1996

9 (31)

Pin description

Pin

Symbol

Function

37

C

Clock line: 2-wire serial bus. This pin is used together with the data input (pin 36) to

transfer data from the microprocessor to the circuit. The last 8 bits, consisting of 5 data

bits and 3 address bits, are accepted by the circuit if, during the high phase at pin 37, a

positive edge on pin 36 takes place.

38

LVIO

Line voltage information output. State indicator of the line voltage, VL, and the supply

voltage, VDD. Indicates to microprocessor whether line voltage VL is present across

the circuit and the supply voltage VDD is sufficiently high. If both conditions are

fulfilled, LVIO is on high level.

39

CO

Clock output. Output 455 kHz clock pulse for the microprocessor. The 455 kHz clock

signal generated in the circuit is amplified and sent to CO. This signal is delivered to

the microprocessor as a clock signal. Various internal signals can be output to CO in

test mode.

40

RESET

Reset signal for periphery. A reset signal (active low) is generated to clear all registers

of the circuit. This can be tapped by peripheral modules, particularly by the micropro-

cessor. This pin enables synchronous resetting of the circuit and peripheral modules.

41

XCK

Clock signal generator. Connector for ceramic resonator (455 kHz). The clock for the

digital part of the circuit is generated by a one-pin oscillator, the frequency of which is

determined by the ceramic resonator.

42

ESI

Input for external supply information. Input to indicate the operating state external

supply. In the case of VSA supplied by a power supply unit, the supply source is con-

nected directly to ESI. ESI is connected to VSA by an external diode in forward mode.

The ESI voltage will be one forward voltage higher than the voltage on VSA. This

voltage causes the circuit to be in external supply mode.

43

ZCO

Zero crossing output in ringing phase. ZCO operates when the ringer voltage, VRI, and

the supply voltage, VSA, are sufficiently high. The output voltage ZCO changes state

each time the rectified AC signal of THA crosses the ringing detect turn–on and turn–

off thresholds, thus providing information on the frequency of the ring signal. Further

analysis of the ring frequency is be done by the microprocessor. Secondly, this pin is

used as an input for switching on the test mode. Therefore, a negative voltage of

approximately 1 V must be applied to pin 43.

44

THA

Ringing detection threshold adjustment. Input amplitude and frequency identification.

The rectified ringing voltage is present at this pin. The circuit evaluates the amplitude

of the rectified voltage at THA and the supply voltage VSA (pin 13 ). If both voltages

exceed certain thresholds, the signal present at THA is converted to a rectangular–

pulse signal and is sent via pin 43 to the microprocessor. If the frequency is in the

required range, the microprocessor initiates transmission of the ringing signal. The start

threshold can be raised with a resistor connected in series to pin 44.