The MCU automatic alarm system, which is based on a MODEM (modem) chip, enables remote transmission of alarm information through the factory's internal telephone network or even the public telephone exchange network, regardless of time or location. This ensures a safe, fast, and accurate communication process.
SSI73K222AL is a highly integrated single-chip MODEM developed by TDK Corporation. It offers a range of advanced features that make it ideal for various applications, especially in automated alarm systems. Key characteristics of this chip include:
- Compatibility with 8048 or 89C51 microcontrollers, with a simple interface circuit.
- Support for serial port data transmission.
- Operation in both synchronous and asynchronous modes, including V.22 expansion speed.
- Compliance with CCITT V.22, V.21, BELL 212A, and V.103 standards.
- Built-in functions such as call progress detection, carrier detection, answer tone recognition, and loopback testing.
- Ability to generate DTMF signals and defensive tones at 550 Hz and 1800 Hz programmatically.
- Automatic gain control with a dynamic range of up to 45 dB.
- Utilization of CMOS technology, resulting in low power consumption and a single power supply.
The SSI73K222AL comes 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’s internal state and the microcontroller. The DR register is a read-only register used to monitor the modem’s operational status. The TR register controls the generation of audio signals, allowing the modem to produce DTMF tones, response tones, and defensive tones. Additionally, TR can manage the RxD pin during the modem’s initialization and when connecting with the other party.
Each register has specific status bits, and their functions and usage are detailed in Table 1-27. For more detailed information, refer to the TDK 1997 MODEM datasheet.
When building an MCU-based automatic alarm system, users have three different configuration options to choose from, depending on their specific needs and system requirements.
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