CH224ATF(1999) Ver la hoja de datos (PDF) - Cermetek Microelectronics

Número de pieza

componentes Descripción

Lista de partido

CH224ATF
(Rev.:1999)

Complete 2400 bps Modem Module

Cermetek Microelectronics 

PRELIMINARY

CH224ATF

Label

~RXDTTL

~TXDTTL

~RITTL

~DSRTTL

~CTSTTL

~DCDTTL

~DTRTTL

Table 9. Signal Designations

I/O

Signal Name Designation

The Serial Interface signals are all TTL-level.

OA

Received Data. Active low. 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. Modem responses take priority over

incoming data when the two signals are in competition for ~RXD.

IA

Transmitted Data. Active low. 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. The DTE should hold this circuit in the mark

state when no data is being transmitted or during intervals between

characters.

OA

Ring Indicate. Active low. ~RI output ON (low) indicates the presence

of an ON segment of a ring signal on the telephone line. The modem will

not go off-hook when ~RI is active; the modem waits for ~RI to go

inactive before going off-hook.

For US models, ~RI will respond to ring signals in the frequency range of

15.3 Hz to 68 Hz. The ring signal cycle is typically two seconds ON,

four seconds OFF. The OFF (high) condition of the ~RI input should be

maintained during the OFF segment of the ring cycle (between rings) and

at all other times when ringing is not being received.

OA

Data Set Ready. Active low. ~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.

If the AT&S1 option is selected, ~DSR will come ON in the handshaking

state when carrier is detected in the originate mode or when carrier is first

sent in the answer mode. In addition if a test mode is entered (AT&T1,

AT&T3, AT&T6-AT&T8), ~DSR will go off while the test is running.

~DSR goes OFF if ~DTR goes OFF.

If AT&Q0 and AT&S0 are selected, ~DSR will remain on at all times

regardless of the modem’s current state.

OA

Clear To Send. Active low. ~CTS is controlled by the modem to

indicate whether or not the modem is ready to transmit data. CTS OFF

indicates to the DTE that it should not transfer data across the interface

on TXD. In data modes, the ~CTS output is always ON. In fax modes,

~CTS is optionally used for flow control.

OA

Data Carrier Detect. Active low. When AT&C0 commands is not in

effect, ~DCD output is ON when a carrier is detected on the telephone

line or OFF when carrier is not detected.

~DCD can be strapped ON using AT&C0 command.

IA

Data Terminal Ready. Active low. 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. The

effect of ~DTR ON and ~DTR OFF depends on the &Dn and &Qn

commands. Automatic answer is enabled when ~DTR is ON if the

“Answer Ring count” selectable option is not set to 0. Regardless of

which device is driving ~DTR, the modem will respond to an incoming

©1999 Cermetek Microelectronics, Inc.

8

Document No. 607-0005 Rev.A (11/99)

Share Link: