XECOM (3) XE3301
1 RESET Hardware reset pin, Input, active High, TTL. A high on Pin 1 initiates a hardware
reset. An external reset is not required or recommended. The Reset pulse must be
a minimum of 100 milliseconds long.
2 N/C
3 RXD Received Data, Output, TTL. Serial data output to the host. A logic "High" on RXD
represents a "mark" and a logic "Low" represents a "space".
9 \DTR Data Terminal Ready, Input, active Low, TTL. The "AT&D" command sets the
function of DTR. The default, AT&D2, requires the host to assert DTR to permit a
modem link. The modem drops the call in progress if DTR is revoked and will not
connect until DTR is re-asserted.
10 \LCS Loop Current Sense, active Low Input, TTL. A low on \LCS tells the modem that
loop current is flowing through Tip and Ring. This feature is used only in the
XE3301B version.
11 \CTS Clear to Send, Output, active Low, TTL/CMOS. CTS is used as a Flow Control
output from the modem. The modem revokes CTS with hardware flow control active
to signal the host that the modem's input buffer is full. The modem reasserts CTS
when the buffer can accept more data without a buffer overflow.
12 OH Off-Hook, Output, active High. OH indicates the modem's hookswitch relay is
closed. Hookswitch closure connects the modem to the telephone line.
13 TXD Transmit Data, Input, TTL. Serial data input from the host. A logic "High" represents
a "mark" and a Low represents a"space", TTL.
14 \RTS Request to Send, input, active LOW, TTL. The XE3301 uses RTS for hardware flow
control. When RTS is revoked and hardware flow control is enabled, the modem will
not place data RXD.
15 NC No Internal Connection
16 \RI Ring Indicator, Output, active Low, TTL. When low indicates the modem is receiving
a ring signal.
18 TIP Tip connection to the phone line(RJ11 pin3) from the internal DAA. The XE3301 is
not sensitive to the battery voltage polarity across Tip and Ring.
20 RING Ring connection to the phone line(RJ11 pin4) from the internal DAA.
21 GND Ground (0 volts)
PIN NAME DESCRIPTION
XE3301 Pin Descriptions