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6090D–DRMSD–12-Feb-07

ATSAM3308B

3.2

Sync Bus

The Sync Bus transfers data on a frame basis, typical frame rates being 32, 44.1, 48 or 96 kHz.

Each frame is divided into 64 time slots. Each slot is divided into 4 bus cycles. Each P24 is

assigned a hardwired time slot (8 to 63), during which it may provide 24-bit data to the bus (up to

4 data samples). Each P24 can read data on the bus at any time, allowing inter P24 communica-

tion at the current sampling rate. Slots 0 to 7 are reserved for a specific router DSP, which also

handles audio out, audio in, and remix send.

3.3

Async Bus

The Async Bus has 24-bit data inside the chip and 16-bit data outside.

The P16 processor normally masters the Async Bus; it can read/write the P24 memories and the

external or embedded ROM/RAM. However, each P24 can request a bus master cycle for

accessing external ROM/RAM or other P24 memories. This allows efficient intercommunication

between several P24s on asynchronous block basis. Specific P24 instructions FLOAT and FIX

convert fixed-point DSP data to floating-point 16 bits. This allows for 20-bit audio dynamic range

when using 16-bit external memory.

3.4

16-bit Processor

The P16 processor is widely used in ATSAM products. Using the P16 keeps large firmware

investments from the ATSAM97xx series. A built-in ROM, connected to the P16 holds basic

input/output software (BIOS) for peripherals such as UART, DataFlash, SmartMedia and MPU,

as well as a debugger that uses a dedicated asynchronous serial line. The firmware can reside

on external parallel ROM/Flash or it can be downloaded at power-up into the built-in 16k x 24

RAM from serial EEPROM, DataFlash, SmartMedia or host.

3.5

MMU (Memory Management Unit)

The MMU handles transfer requests between the external or embedded RAM/ROM, the P16

and the P24s through the Async Bus. The ATSAM3308B includes 16k x 24 RAM on chip.

3.6

Router: Final ACC, MIX, Audio Out, Audio In

This block includes RAM (accessed through the Async Bus) that defines the routing from the

Sync Bus to/from the Audio I/O or back to the Sync Bus (mix send). It takes care of mix and

accumulation from Sync Bus samples. Eight channels of audio in and eight channels of audio

out are provided (4-stereo in/out, I2S format). The stereo audio in channels may have a different

sampling rate than the audio out channels. In this case, one (or more) P24 takes care of sam-

pling rate conversion.

3.7

I/O

The ATSAM3308B includes very versatile I/Os, that share common pins for reduced pin count

and small IC footprint. Most I/Os, when not used for a specific function, remain available as firm-

ware controlled general-purpose pins.

The following peripherals are included on chip:

• 2 x 8-bit timers

•2 x 16-bit timers

• Parallel slave 8-bit port, MPU401 compatible

• Parallel master 8-bit port, for connection to SmartMedia and/or LCD display, switches, etc.