New ADI Blackfin Integrates Large Executable Flash for Control Applications

Analog Devices, Inc. (ADI) has announced new members of the Blackfin processor family targeting control-loop applications.  The new BF50x parts sport a much larger “executable” flash in place of the serial flash offered in earlier Blackfin chips, and integrate a 12-bit analog-to-digital converter suitable for control applications.

Previously introduced Blackfin chips rely on serial flash memory (NAND flash using a three-wire SPI interface); data is copied by boot ROM code from the flash memory into the L1 instruction memory before execution.  The new Blackfin BF50x chips instead use a parallel, executable flash (NOR flash using a 32-bit parallel interface connected to the memory controller).  With parallel flash, the flash memory becomes a more integral part of the chip’s memory system.  Code stored in flash can be executed without extra copy operations, using the L1 instruction cache in the same way that external memory would be used. 

The large on-chip parallel flash allows large programs code size to exceed the bounds of the on-chip L1 memory without requiring awkward paging, and therefore enables some applications to eliminate external main memory, reducing cost.  Without the need for external memory, ADI eliminates the external memory interface (EMIF) from the package, reducing pin count, board size, and board complexity.  The BF50x offers up to 4096 KB flash (compared to 512 KB of serial flash in earlier Blackfin parts).  Eliminating the EMIF results in a significant reduction from 168 pins (BF51xF) to 88 pins in the BF504 and BF504F.

In addition, ADI adds a dual 12-bit SAR analog-to-digital converter (2 MSPS) in the BF506F, available with 120 leads.  This provides added integration in the target industrial control applications.  Previously, mixed-signal integration within the Blackfin line was limited to a special-purpose audio codec in the BF52xC family.  According to ADI, the new ADC has the highest effective resolution 12-bit ADC integrated into a microcontroller.

By providing executable flash and eliminating external memory, ADI is aiming new parts squarely at control-loop applications such as motor control.  Earlier Blackfin chips targeted mobile lifestyle, industrial and instrumentation, portable medical diagnostic and VoIP telephony applications.  In control-loop market, ADI will compete primarily against microcontrollers and DSP-enhanced microcontrollers with significantly lower DSP performance.  The BF50x line is priced similarly to the BF51x line, but the lower pin count and lack of external memory is intended to reduce total board cost.  Prices for the new BF50x line range from $5.18-12.78, compared with $6.26-14.07 for the BF51x line (at 1, 1000 units).

The competition in this market comprises microcontrollers (MCUs) and digital signal controllers (DSCs), both of which characteristically integrate flash memory—often eliminating the external memory bus.  Compared to MCUs, DSCs feature higher DSP performance, achieved through specialized architectural features such as dedicated multiply-accumulate instructions.  Both MCUs and DSPs typically use small packages with 60-128 leads.  Additional common features include PWM ports for motor control, as well as a wide range of serial interfaces.  Some products offer a CAN bus or USB port. The Blackfin BF50x chips include 2 UARTs, 2 SPORTS, 2 SPI, 1 I2C, a CAN interface and a PWM unit.

A few competing DSCs, such as the Renesas SH-2A family, utilize dual-multiply-accumulate architectures with total performance of up to 400 million multiply-accumulates per second (MMACS).  By operating at a frequency much higher than supported by previous flash-based products, coupled with a dual-MAC architecture, the new Blackfin offering offers DSP processor-class performance in a DSC package.  This should be most attractive to industrial equipment designers where better DSP performance can lead to improved performance, added product functionality or efficiency specifications.

Some representative MCUs, DSPs and DSCs are summarized in the table below, alongside the new ADI chips:

The BF50x line is sampling now, with pre-production release in Q2’2010 and production in Q4’2010.