描述 Description

The T7121 HDLC Interface for ISDN (HIFI-64) connects serial communications links carrying HDLC bitsynchronous data frames to 8-bit microcomputer systems. There is an optional transparent mode of operation in which no HDLC processing is performed on user data. The device communicates with the system microprocessor as a memory-mapped peripheral and is controlled by reading and writing 19 internal registers. The chip can be instructed to interrupt the microprocessor when it detects certain events requiring microprocessor attention.

特性 Features

■ Low-cost device for B-channel (64 kbits/s) or D-channel (16 kbits/s) data transport.

■ Optional transparent mode—no HDLC framing is performed.

■ Frame sync (FS) allows a slot-select feature to access an individual time slot in any TDM data stream (e.g., Lucent Technologies Microelectronics Group Concentration Highway Interface [CHI] or subset).

■ Bit-masking option allows effective data rates of 8, 16, 24, 32, 40, 48, and 56 kbits/s.

■ Maximum data rate up to 4.096 MHz.

■ Serial data-transfer pins for direct connection to the Lucent ISDN line transceiver T7250C.

■ Supports IOM2, K2, GCI, and SLD interface.

■ Parallel microprocessor interface with either multiplexed or demultiplexed address and data lines for easy interface with any microprocessor.

■ Single interrupt output signal with seven maskable interrupt conditions.

■ Programmable interrupt modes.

■ Memory-mapped read and write registers.

■ TTL/CMOS compatible input/output.

■ 3-state output pins to assist system diagnostics.

■ Low-power 1.25 μm CMOS:

— 30 mW typical operation at 12 MHz.

— 5 mW standby mode (typical).

■ HDLC transceiver:

— Stand-alone HDLC framing operation.

— 64-byte FIFO in both transmit and receive directions.

— Supports block-move instruction.

— Multiple frames allowed in FIFO.

— Programmable FIFO full- and empty-level interrupt.