The ROM code supports booting from SD cards under the following conditions:
- SD cards compliant with SD Specifications Part 1 Physical Layer Specification Version 4.00and the SD Specifications Part 2 File System Specification Version 3.00 from the SD Association. These include low- (SDSC) and high-capacity (SDHC) cards.
- SD card connected to MMC1 controller I/Os. Only one card is allowed to be connected to the bus.
- 3-V VCC power supply
- 3-V or 1.8-V I/O voltages
- Initial 1-bit MMC mode, optional 4-bit mode
- Clock frequency:
- Identification mode: 400 kHz
- Data transfer mode: 10 MHz (optionally up to 19.2 MHz by Configuration Header)