Features • • • • • • • • • • • 16 Multiplier-Accumulators 16 Bit Data and 12 Bit Coefficients, 32 Bit Internal Accuracy 16 Banks of 12 Bit Coefficients 16 Taps at 33 MHz Up to 32 Taps for Symmetrical or Interleaved Zeroed Coefficient Filters at 33 MHz Up to 63 Taps for Symmetrical Halfband Filters at 33 MHz Programmable Decimation by 2, 4, 8 or 16 Cascadable Keeping Symmetry Advantages Output Gain Multiplier Programmable Microprocessor Interface 208-pin QFP Package Programmable FIR Filter Description The AT76C002 FIR filter contains 16 multiplier-accumulators which enable it to implement a 16th order non-symmetrical FIR filter or a 32nd order symmetrical FIR filter, operating at 33 MHz. Furthermore, it can be configured to implement a 64th order filter where the even order coefficients are zero, also running at 33 MHz. The incoming samples are 16 bit coded, the coefficients are 12 bit coded and the internal accuracy is 32 bits. The AT76C002 contains 16 banks of 2 bit coefficients that can be selected in one clock cycle. These banks can also be used to perform decimation by 2, 4, 8 or 16 using FIR filters from 32 taps up to 256 taps. In decimation mode, the symmetry capabilities cannot be used. In order to implement long FIR filters at the highest frequency (i.e. 33 MHz) the circuit can be cascaded, with no limits except the internal accuracy. Symmetry properties can be used in cascade mode. This halves the number of cascaded circuits to implement symmetrical filters. In order to increase the accuracy of the intermediate results, the AT76C002 includes an output gain multiplier which enables the whole 12 bit dynamic of the coefficients to be used. Cascadability cannot be used in decimation mode. The AT76C002 includes a 16 bit microprocessor interface that can be configured to be Intel or Motorola compatible. Applications • • • • High sample rate digital filtering Image processing Video processing Matrix multiplication AT76C002 Block Diagram Backward Delay Line FXP Forward Delay Line ALU ALU Register Register ALU Register Coefficient Bank BXN FXN ALU Register Coefficient Bank Mux BXP Register Coefficient Bank Register Coefficient Bank Register Register Adder Array Mux Register GAIN 0 to 8-bit Down Shifter Register Decimation Dual-Port RAM Mux Timing and Control 8-bit Down Shifter Register Decimation Control Mux Micro Interface ADR RD DATA WR/DS CS Register RESET Mux CLOCK PRA Register Control Unit Configuration Register Output Gain Register DOUT Internal Structure FIR Structure Decimation The AT76C002 is built around an array of 16 17x12 multiplier-accumulators, a forward and a backward delay line which enable FIR filters of up to 32 taps to be implemented with odd and even symmetry. FIR filters with interleaved zeroed coefficients (such as half-band filters) are handled in an efficient way since a 64 tap half-band symmetrical FIR can be implemented in only one device. Using these coefficient banks, the AT76C002 can implement decimation filters by 2, 4, 8 or 16, the output rate being 2, 4, 8 or 16 times lower than the input rate. The value of the decimation is programmed in an internal configuration register using the microprocessor interface. Using the SEN Sample Enable input signal, the circuit can handle a variable incoming data rate. Coefficient Banks Cascadability The AT76C002 contains 16 banks of 12 bit coefficients that can be selected by writing to an internal register. The 12 bit coefficients are loaded using the 16 bit microprocessor data bus where the least significant 12 bits are for the coefficient and the most significant 4 bits are for the address within the bank. The bank number is selected by writing to a configuration register. The ATC76C002 can be cascaded in order to implement long high-rate FIR filters. Even in a cascaded structure, the AT76C002 can efficiently handle symmetrical and interleaved zeroed coefficient FIR filters, by cascading both forward and backward delay lines. In that way, a 128 tap symmetrical FIR filter or a 256 tap symmetrical half-band FIR filter would only require two cascaded AT76C002 devices. 2 AT76C002 AT76C002 Pin Description Arithmetic Precision Name Function VCC Supply voltage GND Ground CLOCK Clock input The AT76C002 includes several features to tune the dynamic of the output results. First of all, the 32 bit output of the FIR structure can be divided by 256 (8 bit down shifter), divided by 1 to 256 (0 to 8 bit down shifter), and then bits 23 to 8 of the data can be multiplied by a 10 bit gain. All features are accessible via the microprocessor bus. These features are useful in cascade mode because, in long filters, most of the coefficients are very low compared with the central ones. Consequently, in a cascade chain, for a device which implements a part of the filter with low coefficients, the coefficients can be tuned in order to use as much as possible the whole 12 bit dynamic. The result is then re-tuned before being transmitted to the next device in the cascade chain. CKEN_SYNC Synchronous clock enable input CKEN Asynchronous clock enable input RESET Master reset input ADR 3 bit microprocessor interface input address bus DATA 16 bit microprocessor interface bidirectional data bus RD Microprocessor interface read input WR/DS Microprocessor interface write/data strobe input CS Microprocessor interface chip select input MOTO/ nINTEL Microprocessor interface configuration selection input SEN Sample enable input FXP 16 bit forward delay line input (for cascadability) FXN 16 bit forward delay line output (for cascadability) BXP 16 bit backward delay line output (for cascadability) BXN 16 bit backward delay line input (for cascadability) PRA 32 bit intermediate result input bus (for cascadability) SF 2 bit output configuration input bus DOUT 32 bit filter output bus OUT_DEN Output data valid ENA0 Least significant 16 bit data out enable (active high) ENA0_N Least significant 16 bit data out enable (active low) ENA1 Most significant 16 bit data out enable (active high) ENA1_N Most significant 16 bit data out enable (active low) Microprocessor Interface The AT76C002 contains a 16 bit microprocessor interface which can be configured, using the MOTO/nINTEL input, to have a Motorola or Intel compatible protocol. In Motorola mode, the protocol uses CS (Chip Select), DS (Data Strobe) and RDW (Read/nWrite) signals. In Intel mode, the protocol uses CS (Chip Select), DS/WR (Write) and RDWR (Read) signals. 3 Electrical Specifications Absolute Maximum Ratings DC Characteristics Symbol Parameter Min Max Unit Conditions VDD DC supply voltage -0.5 5.5 V VI DC input voltage -0.5 VDD + 0.5V V or see +-IIk VO DC output voltage -0.5 VDD + 0.5V V or see +-IOk +-IIk DC input diode current 10 mA VI < -0.5V VI > VDD + 0.5V +-IOk DC output diode current 20 mA VO < -0.5V VO > VDD + 0.5V IOLMAX Continuous output current 10 mA Industrial IOHMAX Continuous output current 10 mA Industrial TSH Time of outputs shorted 5 sec TA Temperature range -40 +85 C TSG Storage temperature -65 +150 C Industrial Symbol Parameter Min Max Unit Conditions IIH Input leakage, no pullup -1.0 +1.0 µA VIN = VDD = 5.5V IIL Input leakage, no pullup -1.0 +1.0 µA VIN = 0 VDD = 5.5V IOZ Highimpedance output current bi-directional pins -1.0 +1.0 µA VDD = 5.5V VIL Low level input voltage 30% VDD V CMOS inputs and bi-dir VIH High level input voltage V CMOS inputs and bi-dir VOL Low level output voltage V IOL = 5.0 mA VOH High level output voltage V IOH = 5.0 mA CIN Input capacitance 70% VDD 0.5 VDD 0.5V 7 pF Recommended Operating Conditions Symbol Parameter Min Typ Max Unit VDD DC supply voltage Conditions 4.5 5.0 5.5 V VI DC input voltage 0 5.0 VDD V VO DC output voltage 0 5.0 VDD V TA Temperature range -40 +85 C Industrial TR Input rise time 15 ns 10% - 90% CMOS TF Input fall time 15 ns 10% - 90% CMOS © Copyright Atmel Corporation 1996. Atmel Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in an Atmel Corporation product. No other circuit patent licenses are implied. Atmel Corporation’s products are not authorized for use as critical components in life support devices or systems. Atmel Headquarters, 2325 Orchard Parkway, San Jose, CA 95131, TEL (408) 441-0311, FAX (408) 487-2600 Atmel Colorado Springs, 1150 E. Cheyenne Mtn. Blvd., Colorado Springs, CO 80906, TEL (719) 576-3300, FAX (719) 540-1759 Atmel Rousset, Zone Industrielle, 13106 Rousset Cedex, France, TEL (33) 42 53 60 00, FAX (33) 42 53 60 01 Terms and product names in this document may be trademarks of others. Printed on recycled paper. 0676A/76C002-A-9/96/15M