Abstract: Introduced uses multi-pattern modem chip CMX868 to be able directly carries on through the high speed serial main line and the monolithic integrated circuit serial interface corresponds this characteristic design set to use the monolithic integrated circuit to control the CMX868 chip the data transmission system. The test result indicated that this system can realize the signal in network correct transmission, but widely applies in the data acquisition, the telemetering and so on each domain.
Key word: CMX868; Multi-pattern modem; Serial main line; Telemetry system
American Consumer Microcircuit Limited MX-COM Inc. Corporation develops new product CMX868 is one kind of new multi-pattern modem chip. May apply in the low voltage V.22bis modem’s design. CMX868 chip function in China, because very little has the related introduction not to obtain the full development, this article introduced that develops a set of communication facility’s design proposal with the monolithic integrated circuit and this modem chip and the related hardware. Because this design is not very high (only needs indefinite tense to the terminal performance requirement or receives 0~9999 between to outside transmission the data), therefore (e.g. AT89C51) does not construct one from the price to the PC machine 1/10 monolithic integrated circuits to be able to control the modem chip behavior the terminal system then to satisfy requests, moreover can also reduce equipment’s operating cost greatly.
1 system principle of work
1.1 CMX868 main chips
The CMX868 multi-pattern modem is one kind of low voltage V.22bis modem chip, very suitably in embedded system. It uses the low geometry CMOS technology, the normal work voltage is 2.7V, the operating current is 5A, time the same condition’s power loss is zero. CMX868 supports V.22, Bell 212A 煟 Zheng 23 煟 to gather together peaceful yu 202 煟 Zheng 21 and so on agreements, the highest transmission speed is 2400bps. Carries on the establishment to its internal parameter register to be possible to cause this chip by the specific agreement and the outside correspondence. But this establishment will affect the signal modulation demodulation the way, simultaneously was also deciding in the course of communications uses signaling system.
1.2 signal transmissions
CMX868 data signal’s in system transmission route as shown in Figure 1. And, CMX868 and the monolithic integrated circuit are connected through the serial port, the chip often is in “the zero status” the waiting pattern, the current sinking is only 1μA. With the bell signal may the zero status under CMX868 activation, cause it thrust build-up. The CMX868 chip may produce signal of stop IRQN informs the monolithic integrated circuit permission after its receive data-, again through monolithic integrated circuit’s P1.0 pin (and on CMX868 CSN connected) and T1 pin (and on CMX868 SERIAL CLOCK connected) to CMX868 sending signal. When they simultaneously are in “enables” the condition, the data and the address then separately through COMAND DATA and REPLY DATA these two data lines carry on the transmission.
Figure 2
The former design usually is separately is connected the bell examination electric circuit and the double thread interface circuit with CMX88 and the telephone line.
But this design both conformity is a whole, thus simplified the electric circuit, enhanced system’s reliability.
2 hardware designs
Shown in Figure 2 is which the author designs based on the CMX868 Modem system circuit, this circuit design has referred to the overseas related principle of design and thought [1]~[4], simultaneously also considered factors and so on domestic part origin.
The print circuit wafer’s design may use software protel99se to complete, and may after completing the principle design induct the network table, the layout, the wiring, thus completes the print circuit wafer the manufacture.
3 software designs
This system’s primary mission is carries on the hypothesis to the CMX868 chip initialization and communication link’s parameter, after simultaneously will gather the information to carry on the information decoding which, the code transmission and will receive songzhi display system. System’s main program flow may divide into “the message routing” and “the information receive” two relatively independent parts, Figure 3 and Figure 4 respectively is this system data transmission and the receive software flow chart, its procedure may use the C language establishment. Because the data receive and the sending process are cut unceasingly, therefore, when it is at “the receive information”
the condition, because does not know the receive information the data quantity, therefore the possible need procedure to make the judgment to the receive information, so that after being able to receive the preinstall the information ending carries on the pattern again the transformation. Moreover, the CMX868 initialization and communication link’s parameter hypothesis is only when the system adds the electricity start is essential, thus in schema translation time does not need to duplicate.
4 test results
This system debugging (system A) and “the two overnight stays” (system B) between carries on “the source”. When debugging, first completes two set of system’s electric circuit characteristic tests and the software and hardware jointing shake down testing work separately, afterward carries on A, course of communications debuggings between the B two set of system’s. When enters several 1234 when on the system A keyboard, the system B nixietube demonstrated the data tallies with it, thus confirmed: Develops the system may satisfy the design requirements.
