摘要 |
PROBLEM TO BE SOLVED: To efficiently indicate the number of flags between transmitting frames and frame ending flags from a control part, or notification of information regarding the number of flags between receiving frames and frame ending flags to the control part, in an HDLC mode. SOLUTION: The modem is given a configuration in which a double transmission ring buffers is provided in the modem, and is provided with a first transmission buffer 1b which stores transmitted data of octet unit sent from a terminal device, in a ring form, a data conversion mechanism 1c which converts the transmitted data stored in the first storing buffer 1b to a form to be transmitted on a communication circuit, and a second transmission buffer 1d which stores data converted in the conversion mechanism 1c to be sent onto the communication circuit, in a ring state.
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