CH1786 Family of Ultra Small 2400bps Modems INTRODUCTION FEATURES The CH1786 family of modems are a full function, Supports Standards ITU-U V.22bis,V.22,Bell FCC Part 68 approved 2400bps modem. These 212,and Bell 103 modems provide a fast, easy and flexible way to FCC Part 68 approved and DOT CSA CS-03 Part I integrate a modem into any OEM product while approvable utilizing the minimum amount of PCB space (1.01 x UL 1950 and CSA C22.2 950 Listed 1.27 x 0.52 ). The CH1786 family only requires two external interfaces: a ITU-U V.24 serial interface that UL File Number: E104957 can be routed directly to a UART, and a Tip and Ring AT Command structure with extensions interface which goes directly to an RJ-11 jack for the 1500 VAC RMS isolation barrier minimum, 2122V PSTN line connection. The CH1786 can be peak surge protection minimum controlled with industry standard AT commands and, Single 5 volt operation hence, is compatible with available industry communication software. Low power operation with automatic reduced power standby mode All CH1786 modems support asynchronous operation Automatic adaptive and fixed compromise at 2400bps, 1200bps, and 300bps to both Bell and equalization ITU-U standards. The resident PSTN line interface, Size: 1.01 x 1.27 x 0.52 (nominal) or Data Access Arrangement (DAA), while being FCC approved, is also Canadian DOT approvable and can NVRAM allows storage of custom configurations be approved in other countries that require 1500VAC and telephone numbers RMS isolation requirements per UL 1950 Edition 3. The CH1786 family of modems operate off a single 5- CH1786 FAMILY volt supply. The low power operation and automatic CH1786 NVRAM, Voice/ Inject, Hermetic, standby mode make these modems ideally suited for Operating Temperature: portable equipment. In addition, their small physical 0 C to +70 C size affords maximum flexibility in equipment design. CH1786ET NVRAM, Voice/ Inject, Hermetic, Operating Temperature: -40 C to +85 C CH1786NH Non-Hermetic, Operating Temperature: 0 C to +70 C Figure 1. Functional Block Diagram of CH1786. The CH1786 comes with FCC Part 68 approval and is shipped from the factory with an FCC Part 68 label indicating the registration number and ringer equivalent. This label should be prominently displayed on the end product. Figure 2. Voice/ Data Port Control 2004 Cermetek Microelectronics, Inc. Page 1 Document No. 607-0004 Revision L4 (08/04) Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems AT Command Set. A 40-character command line is DESCRIPTION OF FUNCTIONAL BLOCKS supported. The command line starts with AT and AND DISCUSSION OF BASIC OPERATIONS may contain standard or enhanced commands. The Figure 1 contains a functional block drawing of the commands are compatible with EIA Document CH1786. The CH1786 is a highly integrated, full- TR302.2/88-08006. function modem, comprised of a modulator/ demodulator, controller, NVRAM and an FCC Part 68 Serial Host Interface. The serial interface is a V.24 approved and UL 1950/CSA C22.2 950 listed PSTN (EIA-232) compatible interface. Ten Bits total: 1 start line interface. bit, 1 stop bit, and eight data bits which can be either eight bits with no parity or seven odd or even with Modulation/Demodulation and Modem Controller. parity. The start bit is LOW going. RXD and TXD These functions are provided by a monolithic modem data is non-inverted. See pin description in Table 2. integrated circuit. This IC has built-in facilities to accommodate integrated AT command control and Speaker Interface. The SPK output reflects the contains the necessary resident interfaces for general receiver analog input and provides a signal that can communication and routing to the DAA. be used to monitor call progress. The SPK signal can drive a 300 load directly. Typically, the SPK signal Telephone Line Interface or DAA. The CH1786 is input into an audio power amplifier and the family of modems is designed to meet 1500VAC RMS amplifier, in turn, drives the speaker coil. The isolation and provide 2122V peak surge protection. speaker is activated with the ATMn command. The Consequently, the CH1786 satisfies U.S. FCC Part speaker volume is adjusted using the ATLn 68 and DOT CSA CS-03 Part I Canadian command, where n is 0, 1, 2, or 3. Increasing requirements, and will meet other international numbers correspond to higher volume. Figure 6 approval agency requirements that specify these indicates one method of driving an external 8 levels of isolation. speaker. With the exception of the U.S., most countries Phone Control. Cermeteks CH1786 contains a pin (including Canada) require submission of the final called Voice or Data (V/D). The V/D pin toggles high product or system containing the CH1786 to the appropriate governing regulatory agency for approval. when the modem goes off hook. This pin can be Typically this is accomplished by submitting the final used to activate a relay which can switch a telephone end product to an independent test house or on or off the Tip and Ring incoming PSTN lines. This consultant for evaluation. The test house or feature allows any telephone associated with the consultant then forwards the test results and CH1786 to be disconnected when a data call is in applicable documents to the regulatory agency. Call progress, thereby preventing the data from being Cermetek for a list of suggested consultants. disturbed by an inadvertent telephone pick-up. See Figure 2. Non-Volatile RAM (NVRAM). The NVRAM present on the CH1786 is sufficient to store up to two user Speed and Parity Selection. Prior to call initiation, customized modem configurations. The AT&Wn the host controller trains the modem to the host command will store the active modem configuration in speed (2400,1200 or 300bps) and parity (odd, even, the selected NVRAM locations by specifying an n of 0 mark, space, or none) via a host-initiated training or 1. sequence. This training also sets the speed of the data for originate calls. The CH1786 will The AT&Yn command selects the modem automatically adjust to the originators speed when configurations to be automatically recalled and made answering calls. active upon a reset or power up. The ATZn command immediately recalls and activates a stored The CH1786 matches the hosts parity when it returns configuration. Refer to Tables 4, 5 and 6 for storable status messages to the host. During a data S-Registers and available commands. connection, however, the modem passes parity through without interpretation or alteration. The NVRAM can save up to four telephone numbers with up to 36 digits or modifiers in each telephone Sleep Mode. To minimize power consumption, the number. The AT&Zn=s command will store s, the CH1786 includes a power down feature called Sleep telephone number dial string. The individual NVRAM Mode. When activated, the CH1786 will telephone number storage locations are selected by automatically enter Sleep Mode after 0 to 254 specifying an n of 0, 1, 2, or 3. The ATDTS=n seconds of inactivity. The inactivity delay is selected command will cause the modem to dial the stored using the ATS24 command. The CH1786 is telephone number in location n. NVRAM is not delivered from the factory with a 5 second inactivity available on the CH1786LC or CH1786NH. delay enabled (i.e., ATS24=5). The CH1786 returns SUPPORT FEATURES to normal operation when a ring signal is received or 2004 Cermetek Microelectronics, Inc. Page 2 Document No. 607-0004 Revision L4 (08/04)