Motorola DSP56362
A 24-bit audio DSP that spent its career inside other people's gear. It left a trail of synths and broadcast processors behind it.
Overview
The DSP56362 is a Motorola digital signal processor. It's a chip sold to equipment makers, not a box you plug into a rack. Motorola's own product brief, dated 1999, describes it as "a high performance DSP optimized for cost-sensative consumer audio applications." The misspelling is in the original. This was never a flagship part. It was the workhorse you built a product around.
The numbers tell a familiar story for the 56300 family. The DSP56362 runs its single-clock-per-cycle core at 100 million instructions per second from an internal 100 MHz clock at a nominal 3.3 V, with a faster variant offered at 120 MHz/MIPS. That is a lot of arithmetic for a consumer-audio part, and it explains why the chip turns up in places where real signal processing had to happen cheaply. It is a 24-bit fixed-point design, and the package is a 144-pin plastic Thin Quad Flat Pack — a fine-pitch surface-mount part, not something a hobbyist sockets into a breadboard.
Collectors care about the company this chip kept. It shows up inside Clavia's Nord Lead 2X, where two DSP56362 processors split the voice workload, each DSP handling half of the available voices. They are paired with a Motorola MC68331 running at 25 MHz. It also appears in the Audio Refinement Pre-2DSP, where the chipset is credited with 24-bit processing and speeds up to 100 MIPS. And it turns up in Korg's CX-3, alongside general-purpose microcontrollers and separate tone-generation and effects DSPs.
The period record is thin but real. Audio-Express (April 2001, p.80) gave the part a write-up in Charles Hansen's "New Chips on the Block" column. It describes the on-board software surround decoder, the 100 MHz/MIPS and 120 MHz/MIPS versions at a nominal 3.3 V, and the chip's role as the centerpiece of Motorola's Symphony® Surround Module application. That article is essentially the only contemporary press coverage the Archive has located.
Key Features
On-Board Software Surround Decoder
The DSP56362 carried a software surround decoder on board. That is unusual for a general-purpose audio DSP, and it explains its placement in consumer A/V designs. Motorola positioned a general-purpose version alongside a multimode, multichannel audio decoder variant aimed at A/V receivers, surround-sound decoders, DVD players, and digital TV. A single chip that could decode multichannel formats without an external decoder was worth real money in those products. The on-board decoder is what separates the DSP56362 from a plain 56300-core DSP.
Single-Clock-Per-Cycle DSP56300 Core
Underneath the audio peripherals sits the DSP56300 core. Motorola built it around a single-instruction-per-clock-cycle architecture and kept it code-compatible with the earlier DSP56000 core family. That mattered to a product designer, because existing 56000-family code could move onto the 56362 without a rewrite. The core is why the chip could be described as a 24-bit audio DSP running at 100 MIPS at 3.3 V. That arithmetic headroom let it handle compression, decompression, sound-field processing, and acoustic equalization in the same device.
24 × 24 + 56 → 56-Bit MAC with Dual Accumulators
The data ALU does the audio math. Motorola gave it a 24 × 24 + 56 → 56-bit multiply-accumulate with two 56-bit accumulators. For a 24-bit part, that extra accumulator width is the difference between a filter that stays clean after thousands of recursive operations and one that piles up rounding error until you can hear it. Two accumulators let the core pipeline results without dumping to memory between every operation.
3K × 24-Bit Program RAM and Factory-Programmed ROM
The DSP56362 carries 3K × 24-bit program RAM on chip. Motorola also offered program ROMs that could be factory programmed with data or program provided by the application developer. A manufacturer with a fixed decoding algorithm could have Motorola burn it in, saving the cost and board space of an external ROM. The RAM is what a designer used for code that had to change, or for the control parameters the host CPU pushed down at runtime.
Six Serial Data Lines, Master or Slave
The DSP56362 exposes six serial data lines. Four are selectable as receive or transmit, and two are transmit-only. It can operate as either master or slave on those lines. A designer who needs four inputs and two outputs gets them, and one who needs the chip to drive the clock rather than follow it can have that too.
OnCE, JTAG, and Address Trace Debugging
Motorola gave the DSP56362 a full debug suite: an On-Chip Emulation (OnCE) module, a JTAG Test Access Port, and an Address Trace mode. OnCE lets an emulator halt the core, inspect registers, and step through code without pulling the chip out of the board. JTAG handles boundary-scan testing. Address Trace records where execution has been. For a part aimed at cost-sensitive consumer gear, that is a serious development-tooling commitment, and it helps explain why smaller audio firms adopted the chip. They could not afford to build their own debug infrastructure.
144-Pin TQFP Package
The DSP56362 ships in a 144-pin plastic Thin Quad Flat Pack, a fine-pitch surface-mount package. It is not socketable, not hand-solderable without real skill, and not something you swap on a whim. It is still the correct package for the job. A consumer-audio DSP has to fit on a dense board next to converters and analog stages, and a thin quad flat pack gets 144 pins onto a board without eating the space a bigger package would demand.
Historical Context
Motorola designed the DSP56362 to support digital audio applications requiring digital audio compression and decompression, sound-field processing, acoustic equalization, and other digital audio algorithms — a broad brief that explains why the part ended up in such different products. The chip was the centerpiece of Motorola's Symphony® Surround Module application, a reference design built jointly with AKM Semiconductor around the DSP56362 and several AKM components, aimed at low-cost digital audio decoder systems. That reference design is the clearest statement of intent: Motorola wanted the 56362 to be the decoding brain in a whole generation of consumer A/V gear.
The part was documented in the audio press in early 2001, and Audio-Express (April 2001, p.80) is the source for the Symphony Surround Module framing and the 100 MHz/MIPS and 120 MHz/MIPS variants. Motorola has since introduced the DSP36366 (120 MIPS) and DSP36367 (150 MIPS). Those designations are printed as they appear in the surviving sources and should be verified against primary datasheets before quoting. No production years, original price, or official data sheet for the DSP56362 itself have surfaced in the Archive's research, so the timeline of the part's commercial life remains an open question.
The record does confirm the design-win trail. Clavia's Nord Lead 2X used two DSP56362 processors at 120 MHz alongside a Motorola MC68331 at 25 MHz, splitting the voice workload between the two DSPs. The Audio Refinement Pre-2DSP used the Motorola DSP56362 chipset, with 24-bit processing and speeds up to 100 MIPS. The Korg CX-3 carried a tone-generation DSP and an effects DSP among its processing hardware.
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