In SD boot modes, MIO[26, 29, 30:33] for SD1 (2.0), MIO[26:27, 29:36] for SD1 (3.0), or MIO[38, 40:48] for SD0 (3.0) are configured by the BootROM to use:
- Default drive strength (8 mA)
- Default slew rate (slow)
- Default weak pull-ups (enabled)
- Enables the Schmitt trigger
- Disables the 3-state control
The remaining MIOs are not set by the BootROM and remain at their default state. If a secure lockdown occurs during boot, the BootROM sets the PMC_GLOBAL TRISTATE_OVERRIDE register to force all I/Os into a tristate mode. This register is then reserved for use by the PLM firmware.
The following table lists the bidirectional PMC multiplexed I/Os (MIOs) and their functions used in the SD boot mode setup.
| PMC MIO Pin | Signal Name | Description |
|---|---|---|
| 26 | SD1_CLK | SD1 clock output. |
| 29 | SD1_CMD | SD1 command. |
| 30 | SD1_DATA[0] | Data pin used in SD1 boot mode. |
| 31 | SD1_DATA[1] | Data pin used in SD1 boot mode. |
| 32 | SD1_DATA[2] | Data pin used in SD1 boot mode. |
| 33 | SD1_DATA[3] | Data pin used in SD1 boot mode. |
| 28 | SD1_DETECT | Provides a card detect input that reflects the state of the mechanical switch on the SD card. The card detect signal is not required for primary boot. Not supported by BootROM. |
| 50 | SD1_WP | Write protect input signal. The write protect signal is not required for primary boot. Not supported by BootROM. |
| 51 | SD1_BUSPWR | Bus power output that can be used to gate or reset the SD card power on the board. The bus power signal is not required for primary boot. Not supported by BootROM. |
| PMC MIO Pin | Signal Name | Description |
|---|---|---|
| 26 | SD1_CLK | SD1 clock output. |
| 29 | SD1_CMD | SD1 command. |
| 30 | SD1_DATA[0] | Data pin used in SD1 boot mode. |
| 31 | SD1_DATA[1] | Data pin used in SD1 boot mode. |
| 32 | SD1_DATA[2] | Data pin used in SD1 boot mode. |
| 33 | SD1_DATA[3] | Data pin used in SD1 boot mode. |
| 34 | SD1_SEL | Select signal output is automatically asserted when SD3.0 mode is selected. Select signal enables an external voltage translator to switch from 3.3V to 1.8V to operate the SD card at the highest performance supported. |
| 35 | SD1_DIR_CMD | DIR CMD output determines if the command is an input or output. |
| 36 | SD1_ DIR0 | DIR0 output determines if Data[0] is an input or output. |
| 27 | SD1_DIR1 | DIR1 output determines if Data[3:1] direction is an input or output. |
| 28 | SD1_DETECT | Provides a card detect input that reflects the state of the mechanical switch on the SD card. The card detect signal is not required for primary boot. Not supported by BootROM. |
| 50 | SD1_WP | Write protect input signal. The write protect signal is not required for primary boot. Not supported by BootROM. |
| 51 | SD1_BUSPWR | Bus power output that can be used to gate or reset the SD card power on the board. Not required for primary boot. BootROM configures the bus power signal in SD1 (3.0) boot mode. |
| PMC MIO Pin | Signal Name | Description |
|---|---|---|
| 38 | SD0_CLK | SD0 clock output. |
| 40 | SD0_CMD | Command signal. |
| 41 | SD0_DATA[0] | Data pin used in SD0 boot mode. |
| 42 | SD0_DATA[1] | Data pin used in SD0 boot mode. |
| 43 | SD0_DATA[2] | Data pin used in SD0 boot mode. |
| 44 | SD0_DATA[3] | Data pin used in SD0 boot mode. |
| 45 | SD0_SEL | Select signal is automatically asserted when SD3.0 mode is selected. Select signal enables an external voltage translator to switch from 3.3V to 1.8V to operate the SD card at the highest performance supported. |
| 46 | SD0_DIR_CMD | DIR_CMD output, determines if the command is an input or output. |
| 47 | SD0_DIR0 | DIR0 output determines if Data[0] is an input or output. |
| 48 | SD0_DIR1 | DIR1 output determines if Data[3:1] direction is an input or output. |
| 39 | SD0_DETECT | Provides a card detect input that reflects the state of the mechanical switch on the SD card. The card detect signal is not required for primary boot. Not supported by BootROM. |
| 37 | SD0_WP | Write protect input signal. The write protect signal is not required for primary boot. Not supported by BootROM. |
| 49 | SD0_BUSPWR | Bus power output that can be used to gate or reset the SD card power on the board. Not required for primary boot. BootROM configures the bus power signal in SD0 (3.0) boot mode. |