The MCU automatic alarm system, built around a MODEM chip, enables remote transmission of alarm information through the factory’s internal telephone network or even the public telephone exchange, regardless of time or location. This ensures a safe, fast, and accurate communication solution.
SSI73K222AL is a single-chip MODEM developed by TDK Corporation, offering high integration and versatility for various applications. Key features of this chip include:
â— Compatibility with 8048 or 89C51 microcontrollers, making it easy to interface;
â— Support for serial port data transmission;
â— Operation in both synchronous and asynchronous modes, including V.22 expansion speed;
â— Compliance with CCITT V.22, V.21, BELL 212A, and V.103 standards;
â— Built-in functions such as call progress detection, carrier detection, answer tone recognition, and long loop testing;
â— Ability to generate DTMF signals and defensive tones at 550 Hz and 1800 Hz programmatically;
â— Automatic gain control with a dynamic range of up to 45 dB;
â— CMOS technology for low power consumption and single-supply operation.
The SSI73K222AL is available in a 28-pin DIP package, as shown in Figure 1-102.
This chip contains four internal registers for control and status monitoring. The CRO register manages the data transmission mode on the telephone line, while CR1 controls the interface between the SSI73K222AL and the microcontroller. The DR register is read-only and provides status information about the MODEM's operation. The TR register is responsible for generating audio signals, including DTMF, response tones, and defensive tones. Additionally, TR controls the RxD pin during startup and when connecting with the other party.
Each register has specific status bits that provide detailed information about the chip’s current state. A brief description of these bits and their usage is provided in Table 1-27 (for more details, refer to the TDK 1997 MODEM datasheet).
When designing an MCU-based automatic alarm system, users have three different configuration options to choose from, depending on their specific application requirements.
Table 1-27 outlines the functions and usage of each status bit in the SSI73K222AL register.
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