There are two bridges on the SAM3U: one for low-speed peripherals with Peripheral DMA Controller (PDC) support, and one for high-speed peripherals with central DMA support (SSC, HSMCI and SPI). The two different bridges mean two different slaves on the system, which allow fetch from the internal SRAM or internal Flash and at the same time perform a transfer from the MMC to MC card or SD card. Thanks to the 5-layer bus matrix, the user is able to parallelize different transfers and thus can connect five different masters to up to ten different slaves.