XE2420-ITR Просмотр технического описания (PDF) - Unspecified

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XE2420-ITR

The World’s First Complete PLCC Packaged Modem

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XE2420 Pin Descriptions (continued)

PIN NAME DESCRIPTION

13 CD/RI

14 /DTR

15 /DCD

16 /DSR

17 /CTS

18 /RTS

19 /RXD

20 /TXD

21 RESET

22 VCC

The CD/RI signal performs two functions in the XE2420 and XE2421. It reports on local

telephone line availibility and the presence of an incoming ring signal. As a steady-state high,

CD/RI indicates that the local telephone line is available for use by the modem. As a steady-

state low, CD/RI indicates that the local telephone line is not available for use by the modem

either because the modem is not connected to the line or because the line is already in use. When

a ring signal is present across Tip and Ring, the CD/RI output toggles at the ring frequency. CD/

RI operates off Vui and therefore operates even when VCC is removed from the modem.

/DTR is an active low input to the modem. The AT&D command determines how the modem

will interpret activity on /DTR.

/DCD is an active low output from the modem. The AT&C command controls when the XE2420

asserts /DCD.

/DSR is an active low output from the modem. The AT&S command controls when the XE2420

asserts /DSR.

/CTS is an active low output from the modem. The modem asserts /CTS to indicate that it can

accept data from the terminal equipment on /TXD.

/RTS is an active low input to the modem. /RTS indicates to the modem that the host has data to

send.

/RXD provides the path for received data and modem responses to be sent from the modem to

the host terminal equipment.

/TXD provides the path for transmitted data and modem commands to be passed from the host

terminal equipment to the modem.

RESET is an active high input which intiates a modem hardware reset. RESET must be active

for a minimum of 100 milliseconds for a proper modem reset sequence. No external reset is

required; if none is used the RESET signal should be left open.

VCC provides 5 volt power to the modem. The Ring Detect circuit is not powered by VCC but

by Vui.

XECOM

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XE2420

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