1200 BPS DCM-212 Modem (260-1385A) Speed Options Faxback Doc. # 7056 The DCM-212 Modem automatically synchronizes with standard speed rates of 300 and 1200 bits per second (bps). Switching from high speed (1200 bps) to low speed (300 bps) operation occurs when the DCM-212 receives either the wake-up code in the Tandy protocol mode or the Attention code in the Hayes protocol mode. When the modem detects 1200 bps after receiving the code sequence, it communicates in high speed. If the modem is awakened at 300 bps, it uses low speed operation. The originating station always determines the speed of operation. If you wake up the DCM-212 in low speed mode but intend to call a high speed modem, the DCM-212 will select the low speed 300 bps operation if the remote modem has low-speed detection circuitry. If you intend to call a high-speed modem, you must set the DCM-212 to high speed before calling a remote modem. COMMUNICATIONS PROTOCOL Certain criteria must be met before computer-to-computer communication can occur. The modem operates on 10 or 11-bit data words. The following combinations are allowed: START BIT DATA BIT PARITY BIT STOP BIT COUNT COUNT COUNT COUNT 1 8 NO 1 1 8 NO 2 1 7 YES 1 1 7 YES 2 1 7 NO 2 The condition of 1 start bit, 7 data bits, no parity bit and only 1 stop bit will be auto recognized as having a marking or spacing 8th data bit. A communication error could result if you do not use at least 10 bits as shown above. If you must operate with fewer than 10 bits, remember that abort sequences, where character recognition is needed, might not operate. Long space disconnect and carrier drops will, however, still operate. When opened for programming by the wake-up or attention code sequence, the DCM-212 automatically synchronizes the speed rate, word length, parity, and stop-bit numbers (communications protocol) of your computer system. NOTE: One modem must be in originate mode and the other must be in answer mode. usually, when you call another computer, you should be in originate mode. When you receive a call, you should be in answer mode. MANUAL V. AUTOMATIC OPERATION When you want to dial an information service (such as CompuServe or Dow Jones News Service) or communicate with another person whose computer is also using VIDTEX, set the modem to manual operation mode. In this mode, you can control what the system does by manually dialing and answering the phone. When you want the DCM-212 to dial a phone number or answer the phone for you, set it to automatic operation mode. In this mode, the modem dials the phone number you store in its memory or answers the phone when someone calls you. Automatic mode, for instance, lets you dial the information service number without picking up the phone--just type the number along with the proper DCM-212 programming commands on the computer keyboard. ORIGINATE V. ANSWER MODE To place a call to an information service or another person using VIDTEX, set the DCM-212 to originate mode. In this mode, the call originates from your computer. When you want to receive a call (answer the phone), set the DCM-212 to answer mode. Note that originate and answer modes can be used either manually or automatically. HELPFUL TIP: When you use your DCM-212 for the first time or when you seem to be getting garbled data, use the self-test mode to help you find the cause of thee problem. Refer to the section on "self-test" in Appendix A, TANDY PROTOCOL REFERENCE, or in Appendix B, HAYES PROTOCOL REFERENCE. If you plan to use the DCM-212 in Tandy protocol mode only, you can skip Chapter 3 and Appendix B. Or, if you intend to use your modem in Hayes mode only, you can disregard Chapter 2 and Appendix A. For further operation information, refer to the operation manual that accompanies your communications software package. (dkh-08/05/093)