CCNP™|CCDP™ Remote Access (642-821) practice questions

EIA/TIA-232 standard

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Q1. In EIA-232 environment, which signal is used by a DTE to indicate that the DTE has buffers available receive data?





Correct Answer: A


In EIA/TIA-232 standard, signals can be grouped as below (Pin numbers are given assuming 25 pin connector cable):
Data Transfer Group:
TxD (pin 2 on DTE): Transmit Data - This represents data transmit from DTE to DCE (Note the reference is DTE)
RxD (pin 3 on DTE): Receive Data - This represents data received from DCE to DTE (Again note the reference is DTE)
GRD (pin 7 on DTE)
Flow Control Group:
RTS (pin 4): Request To Send - Represents that the DTE has buffer space available to receive data from the DCE.
CTS (pin 5): Clear To Send - Represents that the DCE has buffer space available to receive data from DTE.
Modem Control Group:
DTR: Data Terminal Ready - Represents that the DTE is ready to receive data.
CD (pin8) - Carrier Detect - Indicates that the DCE has detected carrier from remote DCE.
DSR (pin6): Data Set Ready - It indicates that the DCE is ready to use.
If you are using a 25 pin connector on either end, and the cable is straight through, there is one to one correspondence in the pin connections. That is pin 2 of DTE is connected to pin 2 of DCE, pin 3 of DTE is connected to pin 3 of DCE etc. However, if you are using 25 pin connector at one end and 9 pin connector at the other end, the pin numbers change. Similarly, if you are using cross connection (like DTE-DTE or DCE-DCE or NULL modem), the corresponding pin connections are not same.

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