RC56D, RC336D, and RC144D Modem Device Sets Designer’s Guide
1154
Conexant
3-13
Table 3-5. MCU Pin Signal Definitions (Cont'd)
Label
I/O Type
Signal Name/Description
V.24 (EIA/TIA-232-E) DTE SERIAL INTERFACE (SERIAL DTE INTERFACE CONFIGURATION)
These signals correspond functionally to V.24/EIA/TIA-232-E signals with TTL levels and are inverted from V.24/EIA/TIA-232-E levels.
~TXD (PA2)
It
Transmitted Data (EIA BA/ITU-T CT103). The DTE uses the ~TXD line to send data to the modem for
transmission over the telephone line or to transmit commands to the modem.
~RXD (PA6)
Ot1.6
Received Data (EIA BB/ITU-T CT 104). The modem uses the ~RXD line to send data received from the
telephone line to the DTE and to send modem responses to the DTE. During command mode, ~RXD
data represents the modem responses to the DTE.
~CTS (PC1)
Ot6
Clear To Send (EIA CB/ITU-T CT106). ~CTS output ON (low) indicates that the modem is ready to
accept data from the DTE. In asynchronous operation, in error correction or normal mode, ~CTS is
always ON (low) unless RTS/CTS flow control is selected by the &Kn command.
In synchronous operation, the modem also holds ~CTS ON during asynchronous command state. The
modem turns ~CTS OFF immediately upon going off-hook and holds ~CTS OFF until both ~DSR and
~RLSD are ON and the modem is ready to transmit and receive synchronous data. The modem can also
be commanded by the &Rn command to turn ~CTS ON in response to an ~RTS OFF-to-ON transition.
~DSR (PC0)
Ot6
Data Set Ready (EIA CC/ITU-T CT107). ~DSR indicates modem status to the DTE. ~DSR OFF (high)
indicates that the DTE is to disregard all signals appearing on the interchange circuits except Ring
Indicator (~RI). ~DSR output is controlled by the AT&Sn command.
~RLSD (PC2)
Ot6
Received Line Signal Detector (EIA CF/ITU-T CT109). When AT&C0 command is not in effect, ~RLSD
output is ON when a carrier is detected on the telephone line or OFF when carrier is not detected.
~TM (PC6)
Ot6
Test Mode Indicate (EIA TM/ITU-T CT142). The ~TM output indicates the modem is in test mode (low)
or in any other mode (high).
~RI (PC5)
Ot6
Ring Indicator (EIA CE/ITU-T CT125). ~RI output ON (low) indicates the presence of an ON segment of
a ring signal on the telephone line.
~DRSOUT (PC3)
Ot6
Data Signaling Rate Indicator. ~DRSOUT is ON (low) when the modem desires or is engaged in the
high speed (4800 bps or higher) mode. ~DRSOUT is OFF (high) otherwise.
~DTR (PD4)
It
Data Terminal Ready (EIA CD/ITU-T CT108). The ~DTR input is turned ON (low) by the DTE when the
DTE is ready to transmit or receive data. ~DTR ON prepares the modem to be connected to the
telephone line, and maintains the connection established by the DTE (manual answering) or internally
(automatic answering). ~DTR OFF places the modem in the disconnect state under control of the &Dn
and &Qn commands.
~RTS (PD6)
It
Request To Send (EIA CA/ITU-T CT105). ~RTS input ON (low) indicates that the DTE is ready to send
data to the modem. In the command state, the modem ignores ~RTS.
In asynchronous operation, the modem ignores ~RTS unless RTS/CTS flow control is selected by the
&Kn command. In synchronous on-line operation, the modem can be commanded by the &Rn command
to ignore ~RTS or to respond to ~RTS by turning on ~CTS after the delay specified by Register S26.
~RDL (PC7)
It
Remote Digital Loop Select (EIA RL/ITU-T CT140). ~RDL input low activates remote digital loop
request. The loop is executed at the speed for which the modem is currently configured.
~AL (PD5)
It
Analog Loop (EIA LL/ITU-T CT141). ~AL input low causes the modem to operate in the analog loop test
mode.
~TXCLK (PA3)
Itpu
Transmit Data Clock. Used for synchronous serial data transfer. Connect also to MDP ~TDCLK.
~RXCLK (PA4)
Itpu
Receive Data Clock. Used for synchronous serial data transfer. Connect also to MDP RDCLK. In serial
DTE configuration, this function is shared with the SCPIRQ input thus serial synchronous mode cannot
be used if the SCP is connected.
Notes:
1.
I/O types:
It, Ix = Digital input; t = TTL compatible input; pu = internal pullup, pd = internal pulldown, s = special, x = crystal input
Ot1.6, Ot6, Ox = Digital output; t = TTL compatible output, 1.6 = 1.6 mA drive, 6 = 6 mA drive, x = crystal output.(see Table 3-8):
Summary of Contents for RC144D
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