| Pin No. | Symbol | I/O | Function |
| 1 | IN+ | Input | Non-inverting Input of the internal opamp. |
| 2 | IN- | Input | Inverting Input of the internal opamp. |
| 3 | GS | Output | Gain Select of internal opamp. The opamp's gain should be set according to the nominal Vdd of the application using the information in Figure 10. |
| 4 | VRef | Output | Reference Voltage. Nominally VDD/2. It is used to bias the input opamp. |
| 5 | CAP | | Capacitor. A O.lmF decoupling capacitor should be connected across this pin and vss. |
| 6 | TRIGin | Trigger Input | Trigger Input. Schmitt trigger buffer input. Used for line reversal and ring detection. |
| 7 | TRIGRC | Open Drain Output / Schmitt Input | Trigger RC. Used to set the (RC) time interval from TRIGin going low to TRIGout going high. An external resistor connected to VDD and capacitor connected to vss determine the duration of the (RC) time interval. |
| 8 | TRIGout | CMOS Output | Trigger Out. Schmitt trigger buffer output. Used to indicate detection of line reversal and/or ringing. |
| 9 | MODE | CMOS Input | 3-wire interface: Mode Select. When low, selects FSK data interface mode 0. When high, selects FSK data interface mode l. See pin 16 (DCLK) description to understand how MODE affects the DCLK pin. |
| 10 | OSCI | Input | Oscillator Input. A 3.579545MHz crystal should be connected between this pin and OSCO. It may also be driven directly from an external clock source. |
| 11 | Osc0 | Output | Oscillator Output. A 3.579545MHz crystal should be connected between this pin and OSCI. When OSCI is driven by an external clock, this pin should be left open. |
| 12 | Vss | | Power Supply Ground. |
| 13 | IC | | Internal Connection. Must be connected to vss for normal operation. |
| 14 | PWDN | Schmitt Input | Power Down. Active high. When high, the device consumes minimal power by disabling all functionality except TRIGin, TRIGRC and. TRIGout Must be pulled low for device operation. |
| | | |