Atmel is shipping a low-cost embedded processor claimed to offer more bandwidth than other ARM9 chips, thanks to parallel buses and distributed DMA. The AT91SAM9263 targets data- and graphics-intensive applications, and is available with an AT91SAM9263-EK evaluation board that supports Linux.
According to Atmel, ARM9-based processors typically max out at 20 Mbps, due to load/store instructions that require at least eighty CPU cycles to transfer a single byte of data between a memory and a peripheral. The AT91SAM9263, in contrast, only uses a claimed 12 percent of its processor cycles during 20 Mbps transfers, and is said to have a total on-chip data transfer bandwidth of 41.6 Gbps.
Atmel credits the AT91SAM9263 SoC's throughput capabilities to its inclusion 27 DMA (direct memory access) channels — including 18 “simple, silicon-efficient, single-cycle,” peripheral DMA controllers, and five DMA controllers that support burst mode data transfers to the USB host.
The chip also features a nine-layer bus matrix, two additional buses for tightly-coupled-memories (TCMs) used for data and instructions, and two external bus interfaces (EBIs) that support gigabyte-plus external memories.
AT91SAM9263 architecture diagram
(Click to enlarge)
The AT91SAM9263 is based on an ARM926EJ-S core running at 200MHz, with a 100MHz system bus. The SoC integrates an impressive variety of on-chip peripheral interfaces, in combinations aimed at the following specific device applications:
- Human interface — Camera, TFT/STN LCD controller, 6-channel AC97 audio, I2S, and a 2D graphics co-processor
- Networking and communications — 12 Mbps USB host and device, 10/100 Ethernet MAC, and a 1 Mbps control area network (CAN), along with four USARTs, two 50Mbps SPI interfaces, CompactFlash, SDIO (MCI), and a two-wire interface (TWI) for connection GPRS, WiFi, and other external wired and wireless communication modules
- Mass Storage — USB host, SD/MMC memory card interface (MCI), and dual external bus interfaces supporting SDRAM, NAND Flash with error code correction (ECC), and CompactFlash/TruIDE for GByte-plus on-board or removable memory such as USB sticks, CompactFlash hard disks, and memory cards
Additional touted features include:
- Eleven-layer Bus plus 96 kBytes on-chip SRAM; “great for Internet radio, GPS navigation, and other time-critical data-intensive applications”
- 11 buses and 96 Kbytes of on-chip scratchpad SRAM that can be partly configured as tightly-coupled data and instruction memory (TCM); The buses provide multiple parallel on-chip data transfer channels and a total on-chip bandwidth of 41.6 Gbps
- Seven dedicated buses run between the DMA controllers of the Ethernet MAC, USB host, camera interface, LCD controller, 2D-graphics co-processor, 2-channel memory to memory DMA controller, and 18-channel peripheral DMA controller (PDC) and on- and off-chip memory
- Two additional buses, one for data and one for instructions, connect the processor with the tightly coupled memories
- Two more buses connect the instruction and data cache controllers to the memories; once the memory address and block size are configured, the DMAs transfer data automatically, with no additional programming required, Atmel claims
- Dual external bus interface allows simultaneous, parallel operation of the ARM9 CPU and graphics processors
- One EBI has dedicated buses to the on-chip 2D graphics co-processor and to the LCD controller
- The second EBI “eliminates the need for the LCD controller and CPU to share memory, and can increase available CPU MIPS by 20-40 percent,” Atmel claims
- “Comprehensive” suite of system and power control functions:
- Includes a main oscillator, two phase lock loops (PLLs), watchdog timer, two real-time timers, reset controller (RSTC), two power on reset units, 8-level priority Interrupt controller (AIC), shutdown controller (SHWDC), four pulse width modulators (PWM), and a periodic interval timer (PIT)
- System clock frequency is scalable and peripheral clocks can be enabled and disabled all under software control, optimizing dynamic power consumption to system requirements, Atmel says
- Whenever the main-supply shuts down, an on-chip power switch automatically switches power from main supply to the backup battery. In battery-backup mode the current drain is claimed to be only 5uA
The AT91SAM9263 is available now, in a 324-ball BGA package. It is priced below $10 in 100K quantities.
Also available is an AT91SAM9263-EK Evaluation Kit that supports both Linux and Windows CE. It comes with bootloader source code and schematics.
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