SDI Technologies SDIO Card Benutzerhandbuch
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SDIO Simplified Specification Version 2.00
44
11. Power
Control
11.1 Power Control Overview
The concept of high-power SDIO cards was introduced in Version 1.10 of the SDIO Specification. Power Control
supports following two features:
• High-Power
Support
SDIO cards created prior to Version 1.10 of the SDIO Specification were limited to a maximum current of
200mA at any time, irrespective of the number or types of functions supported. With the creation of wireless
communication devices in the SDIO form factor, a need was seen to provide more current to accommodate
the higher power requirements of some SDIO cards. Since backward compatibility is a primary concern for
any changes made to this specification, a method was chosen to prevent a high-power card from drawing
excessive amounts of current from hosts designed to only support the SDIO 1.0 cards. Master Power
Control allows standard and high-power cards to be inserted into any host without causing excessive
current damage to the host. It is important to note that there exists the possibility of trying to use a card that
requires high-power in a standard power host and having that card fail to operate. Master Power Control is
supported on a per card basis and available to the host in the CCCR. A high-power card may have a mix of
both high and standard power functions.
200mA at any time, irrespective of the number or types of functions supported. With the creation of wireless
communication devices in the SDIO form factor, a need was seen to provide more current to accommodate
the higher power requirements of some SDIO cards. Since backward compatibility is a primary concern for
any changes made to this specification, a method was chosen to prevent a high-power card from drawing
excessive amounts of current from hosts designed to only support the SDIO 1.0 cards. Master Power
Control allows standard and high-power cards to be inserted into any host without causing excessive
current damage to the host. It is important to note that there exists the possibility of trying to use a card that
requires high-power in a standard power host and having that card fail to operate. Master Power Control is
supported on a per card basis and available to the host in the CCCR. A high-power card may have a mix of
both high and standard power functions.
• Power Selection Support
Not all hosts can supply enough current for all SDIO cards. A host may choose to use the SDIO card in a
lower power mode to increase operation time. Power Selection enables the host to switch the card to a
lower power mode. It is important to note that there exists the possibility of trying to use a standard power
card in a host that does not have enough power to meet the card’s requirement. In this case the card will fail
to operate. Cards supporting Power Selection will enable the widest range of host support. Power Selection
is supported on a per function basis and available to the host in the FBR.
lower power mode to increase operation time. Power Selection enables the host to switch the card to a
lower power mode. It is important to note that there exists the possibility of trying to use a standard power
card in a host that does not have enough power to meet the card’s requirement. In this case the card will fail
to operate. Cards supporting Power Selection will enable the widest range of host support. Power Selection
is supported on a per function basis and available to the host in the FBR.
11.2 Power Control support for SDIO Cards
11.2.1 Master Power Control
SDIO version 1.10 cards indicate their support for the new power control functions with the SMPC (Support
Master Power Control) bit in the CCCR (See section 6.9). Hosts enable the card’s power control functions with
the EMPC (Enable Master Power Control) bit.
SMPC
Master Power Control) bit in the CCCR (See section 6.9). Hosts enable the card’s power control functions with
the EMPC (Enable Master Power Control) bit.
SMPC
can be set to 0 if the card maximum current is less than 200mA and Power Selection (see section 11.2.2)
is not supported. A SDIO version 1.10 card which has SMPC set to 1 shall maintain backward compatibility when
EMPC
EMPC
is set to 0. A SDIO version 1.0 host may not be aware of EMPC, which will remain 0 (its default state).
In the case where EMPC is set to 0, the card total current shall not exceed 200mA. Functions that exceed
200mA shall not set IORx to 1 and TPLFE_OP_MAX_PWR shall be set to 0. If a multi-function card’s total power
exceeds 200mA the card shall not set all IORx to 1, even if all IOEx are set to 1. Some of the functions’ IORx can
be set to 1 as long as the card’s total current is less than 200mA. If the host tries to enable a function (IOEx =1)
that will cause the card’s total current to exceed 200mA, the card shall disable (IORx=0) one or more functions
to keep the card’s total current less than 200mA. Which functions are enabled depends on the design of the card
vendor.
In the case where EMPC is set to 1, the card current can exceed 200mA, up to a maximum of 500mA. Card
should be designed, where possible, to not require the maximum current , thus functioning in as many hosts as
possible with sufficient power.