3.3.1. Power control register, MCIPower

The MCIPower register controls an external power supply. You can switch the power on and off, and adjust the output voltage. Table 3.2 shows the bit assignment of the MCIPower register.

Table 3.2. MCIPower register

Bit	Name	Type	Function
1:0	Ctrl	Read/write	00 = Power-off 01 = Reserved 10 = Power-up 11 = Power-on
5:2	Voltage	Read/write	Output voltage
6	OpenDrain	Read/write	MCICMD output control
7	Rod	Read/write	Rod control
31:8	Reserved	-	-

When you switch the external power supply on, the software first enters the power-up phase, and waits until the supply output is stable before moving to the power-on phase. During the power-up phase, MCIPWR is set HIGH. The card bus outlets are disabled during both phases.

You can set the supply output voltage using the voltage value on the MCIVDD outputs. Because the operating voltage range can be any value between 2.0 and 3.6 volts, the encoding of the voltage bits in the power control register is application-specific.

Note

After a data write, data cannot be written to this register for three MCLK clock periods plus two PCLK clock periods.

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