CH1787(1998) View Datasheet(PDF) - Cermetek Microelectronics

Part Name

Description

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CH1787
(Rev.:1998)

Small Functional Modem

Cermetek Microelectronics 

Cermetek

microelectronics

CH1787 Small Functional Modem

INTRODUCTION

The CH1787 is a small full function modem that is FCC Part

68 approved. It has been designed to be used in

applications where there is little or no controller intelligence

to command the modem. This allows the user to operate

the modem via hardware resources only, not requiring AT

Command execution for basic operation. For those

applications where there is controller intelligence, the

CH1787 operates like a standard AT Command driver

2400bps, V.22bis asychronous modem.

The CH1787 is ideal as a remote modem such as found in

alarm products and in industrial controllers. Upon some

operational event, the modem will dial a prestored telephone

number under pin activation to make a modem connection

with a host or another site. The modem can also be set to

automatically answer incoming calls or manually answer a

call, using an answering pin. A call can be ended via a

hang-up pin.

GENERAL DESCRIPTION OF FUNCTIONAL

BLOCKS

Figure 1 is a functional block diagram of the CH1787. Each

block will be described. The CH1787 is a highly integrated,

full function modem, comprised of a modulator/demodula-

tor, controller, and an FCC Part 68 approved telephone in-

terface, also called a Data Access Arrangement (DAA) and

NVRAM.

Modulation/Demodulation and Control

This Functional Block is comprised of a monolithic modem

integrated circuit, with built-in facilities to accommodate in-

tegrated “AT” command control and resident interfaces for

general communication and routing to the DAA.

Controller

The controller is a programed microprocessor that provides

commands to the modem in response to external pin acti-

vation. The following pins are controlled by the micropro-

cessor and are described in detail in Table 1. These pins

are operational when the modem is in use at 2400bps only.

ANS - Manual Answer Pin Input - Answer mode-

Places modem in answer mode

ORG - Manual Originate Pin Input - Originate mode -

places modem in originate mode

ORA- Automatic Dial Pin Input - Dials one of two

prestored numbers based on TST

TST - Steering Pin Input used with ORA to select the user

stored number or Cermetek test number

HNG- Hang-up Pin Input used to terminate an active

modem connected

AAR- Automatic Answer Pin - used to place the modem

in Auto Answer Mode

See pin description Table 1 for more details.

Cermetek Microelectronics, Inc.

FEATURES

• Supports Standards CCITT V.22bis, V.22,

Bell 212, and Bell 103

• FCC Part 68 approved and DOC approvable

• Does not require a microprocessor to operate

• Pin activated hang-up

• Pin activated answer

• Manual originate and answer pins

• AT Command structure available

• 1000 VAC isolation barrier

• Single 5 volt operation

• Low power sleep mode

• Automatic adaptive and fixed compromise

equalization

• Test modes and diagnostics

• Size: 2.0” x 1.25” x 0.53”

• NVRAM allows storage of custom configurations

and telephone numbers

• Operating temperature 0o-70oC

• Extended temperature -40oC to 85oC order

CH1787ET

Figure 1. CH1787 Functional Block Diagram

Document No. 603-0182 Rev. D (11/98) 1

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