XRT4500 Datasheet, PDF (48/99 Pages) Exar Corporation – MULTIPROTOCOL SERIAL NETWORK INTERFACE IC

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XRT4500
MULTIPROTOCOL SERIAL NETWORK INTERFACE IC
REV. 1.0.7
1.3.2 DCE/DTE - The DCE/DTE Mode Select Pin
The XRT4500 is capable of supporting either the
"DCE" or "DTE" Modes of operation. Setting this in-
put pin "high" configures the XRT4500 to operate in
the "DCE" Mode. Conversely, setting this input pin
"low" configures the XRT4500 to operate in the "DTE"
Mode. A brief description of DCE Mode and DTE
Mode operations are listed below.
FIGURE 16. A SIMPLE ILLUSTRATION OF THE DCE/DTE INTERFACE
DTE
EQUIPMENT
XRT4500
TXD
RXD
TXC
RXC
TXCE
DTR
DSR
DCD
CTS
RTS
LL
RL
RI (or TM)
DCE
EQUIPMENT
XRT4500
Figure 16 presents a very simple illustration of a DCE
Terminal being interfaced to a DTE Terminal. From
this figure, one can make the following observations
about the DCE and DTE Terminals.
The DCE Terminal
The DCE Terminal is responsible for sourcing/gener-
ating all of the following signals.
• RXD - Receive Data (High Speed Signal)
• RXC - Receive Clock (High Speed Signal)
• TXC - Transmit Clock (High Speed Signal)
• DSR - Data Set Ready
• DCD - Data Carrier Detect
• CTS - Clear to Send
• RI (Ring Indicator) or
• TM (Test Mode).
Further, the DCE Terminal is responsible for receiving/
terminating all of the following signals.
• TXD - Transmit Data (High Speed Signal)
• TXCE (or SCTE) - Transmit Clock Echo (High
Speed Signal)
• DTR - Data Terminal Ready
• RTS - Request to Send
• LL - Local Loop-back Indicator
• RL - Remote Loop-back Indicator
Because of this, whenever the XRT4500 is configured
to operate in the “DCE” Mode, then the following con-
figuration conditions are “TRUE”.
• Three “high-speed” Transmitters are enabled, and
• Two “high-speed” Receivers are enabled.
• Four “low-speed” Transmitters are enabled, and
• Four “low-speed” Receivers are enabled.
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