modem
Implementing a Single-Chip Once I was given the task to implement a modem chip, I immediately started to search for the various available types of such chips. The resulting searches gave me a large range of modem chips. The divide between most of the I.C.'s found was whether the modem was so-called single-chip or dual-chip. The latter involves the same circuitry as in the single-chip modem but has another chip dedicated to DSP (digital signal processing) and some memory (both RAM and ROM). These chips were found to be too complex and beyond the scope of our requirements. On the other han
The modem chip selected for this purpose is the MSM6926 produced by OKI. d the single-chip modems found were also divided into two main types, being those with or without a microcontroller. The following is a detailed description of the chip and its various functions:GENERAL DESCRIPTIONThe MSM6926 is OKI's 300 bps single chip modem series which transmit and receive serial, binary data over a switched telephone network using frequency shift keying (FSK). OKI's single chip modem series is designed for users who are not telecommunication experts and are easy to use cost effective alternative to standard discrete modem design. Applications include interactive terminals, desktop computers, point of sale equipment, and credit verification systems. FEATURES* Compatible with ITU-T V. This device provides all the necessary modulation, demodulation, and filtering required to implement a serial, asynchronous communication link. 21 (MSM6926)* CMOS silicon gate process* Switched capacitor and advanced CMOS analog technology* Data rate from 0 to 300 bps* Full duplex (2-Wire)* Originate and Answer modes* Selectable built-in timers and external delay timers possible* All filtering, modulation, demodulation, and DTE interface on chip. The design of the integrated circuit assures compatibility with a broad base of installed low speed modems and acoustic couplers. Other modulation schemes include ASK, BPSK and QAM but FSK was found sufficient in our case. The latter are not numerous and were initially thought to not even be viable, but upon further detailed research such I. 21 series data sets, where the ITU-T V. CMOS LSI technology provides the advantages of small size, low power, and increased reliability.
Common topics in this essay:
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