Monolithic PMOS speech synthesis IC developed by Texas Instruments

DALLAS, June 11, 1978

A new speech synthesis monolithic integrated circuit has been developed by Texas Instruments Incorporated. It marks the first time the human vocal tract has been electronically duplicated on a single chip of silicon. Measuring 44,000 square mils, the chip is fabricated using TI's low-cost metal gate P-channel MOS process, the same used for TI calculator MOS ICs.

The speech synthesis MOS/LSI integrated circuit along with two 128K dynamic ROMs each with the capacity to store over 100 seconds of speech, and a special version of the TMS1000 microcomputer, all TI developed, serve as the main electronics for the new talking learning aid, SPEAK & SPELL™, for seven year olds and up. The new TI consumer product was introduced at the Summer Consumer Electronics Shows in Chicago , June 11-14.

Speech encoding is achieved through pitch excited Linear Predictive Coding (LPC). As the name implies, LPC is based on a linear equation to formulate a mathematical model of the human vocal tract and an ability to predict a speech sample based on previous ones.

Linear Predictive Coding is a technique of analyzing and synthesizing human speech by determining from original speech a description of a time varying digital filter modeling the vocal tract. This filter is then excited by either periodic or random inputs. An on-chip 8-bit digital-to-analog (D/A) converter transforms digital information processed through the filter into synthetic speech.

Codes for twelve synthesis parameters (10 filter coefficients, pitch and energy) serve as inputs to the synthesizer chip. These codes are stored in a ROM and, once decoded by on-chip circuitry, represent the time varying description of the LPC synthesis model.

Inputs to the digital filter take two forms: (1) periodic and (2) random. The periodic inputs are used to reproduce voiced sounds which have a definite pitch such as vowel sounds or voiced fricatives such as Z , B or D . A random input models unvoiced sounds such as S , F , T and SH.

The speech synthesis chip has two separate logic blocks which generate the voiced and unvoiced excitation. Output of the digital filter drives a D to A converter which in turn drives a speaker.

Key to TI's high quality LPC speech synthesizer is an advanced design 10-stage lattice filter which has an integrated array multiplier, an adder coupled to the multiplier output and various delay circuits coupled to the adder output.

With this increased computational sequencing capability and a fast continuous data transfer rate, the multiplier can accept two inputs every five microseconds. Twenty multiply and accumulate operations are needed to generate each speech sample, and the circuit can generate up to 10,000 speech samples per second.

DALLAS, June 11, 2001

SANTA CLARA, Calif. -- Texas Instruments Inc. will exit the dedicated speech-synthesis chip market at the end of this year when it transfers production of its MSP50C6XX family of speech synthesis ICs to Sensory Inc. here.

Terms of the deal were not disclosed, but a Sensory spokesman said the Santa Clara company will have the right to produce TI's latest generation of speech chips. Dallas-based TI retains ownership of its patents, the Sensory spokesman said. 

Sensory will begin supporting new customers immediately, and TI will continue to accept orders for the MSP50C6xx family until the end of 2001, under an agreement announced by the two companies this week. 

A Sensory spokesman said TI's high-quality, low-data-rate speech synthesis chips will be complementary to the company's own speech recognition chips used in toys, games, robots, home automation systems and products for the disabled. He said the company is especially interested in the fact that "TI's low-data-rate speech compression means it takes a smaller amount of memory to do high-quality speech synthesis."

The MSP50C6XX family features five different chips introduced in 1999 and 2000, whose claim to fame is providing the voice box behind Furby, the chatty toy from Tiger Electronics Ltd., a division of Hasbro Inc. of Vernon, Ill. 

The chip family includes a 12.32 MIPS processor for high-quality, low-data-rate speech compression and Musical Instrument Digital Interface (MIDI) music synthesis, with power left over for other processor and control functions. Members of the MSP50C6XX line can store up to 37 minutes of speech and include as much as 64 I/O pins for external interfacing. 

While the newer chips move to Sensory, TI's older speech synthesis chips will be discontinued, according to Craig Dalley, product manager of TI's Analog and Mixed Signal Group. 

The exit from the speech IC business will not have a material impact on earnings, because it represented a relatively small percentage of the company's revenue, said a TI spokeswoman. 

However, TI's departure from the business may have an impact on the speech synthesis market. The company was the first to commercialize speech synthesis products, and its achievements are chronicled on the Smithsonian Speech Synthesis History Project Web site. 

TI entered the market in the mid '70s, when it provided both a speech synthesizer chip and the learning toy known as the Speak & Spell, which was developed and sold by TI's consumer products division. 

At the time, Gene A. Frantz, TI senior fellow and business development manager for the DSP group, was a program manager for the Speak & Spell and led the development team for TI's early speech products. 

The company developed voice synthesizer processors used in a home computer add-on module for programmers to add speech to programs they would write for themselves. Speech synthesis was also employed in The Magic Wand Speaking Reader, which employed bar codes and a small bar code reader to speak passages of the book. The Magic Wand Speaking Reader was introduced before TI discontinued its consumer products division in 1983. 

In later years, the company provided speech chips to other customers for toys, educational products, language translation products, security systems and home monitoring devices.