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SMS01GAF Datasheet(PDF) 27 Page - Numonyx B.V |
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SMS01GAF Datasheet(HTML) 27 Page - Numonyx B.V |
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27 / 61 page  SMSxxxAF, SMSxxxFF, SMSxxxBF SD memory card hardware interface 27/61 4.2 Power-Up The power-up of the SD Memory Card bus is handled locally in each SD Memory Card and in the bus master. After power-up (or after hot insertion) the SD Memory Card enters the Idle state. When in this state, the SD Memory Card ignores all bus transactions until ACMD41 is received (ACMD command type should always be preceded by CMD55). ACMD41 is a special synchronization command used to negotiate the operating voltage range and to poll the cards until they are out of their power-up sequence. In addition to the operating voltage profile of the cards, the response to ACMD41 contains a busy flag that indicates that the power-up sequence has not completed and the card is not ready for identification. The host has to wait (and continue polling the cards in turn) until the bit is cleared (‘0’). The power-up sequence of an individual card should not exceed 1 second. After power-up the host starts the clock and sends the initializing sequence on the CMD line. This sequence is a contiguous stream of logical 1's. It does not exceed 1ms, 74 clocks or the supply-ramp-up-time. Note that the maximum duration is fixed to 74 clocks which is ten clock cycles more than the 64 clocks after which the card is normally ready for communication to eliminate all power-up synchronization problems. Figure 14. Power-Up Diagram 1. Initialization delay = 1ms (max) + 74 clock cycles + supply ramp-up time. 2. Timeout value for initialization process is 1s. VDDmin ai10043 VDDmax Bus master supply voltage Valid voltage range for CMD0, CMD15, CMD55 and ACMD41 commands Valid voltage range for all other commands and memory access Power up time Supply ramp up time Initialization sequence ACMD 41 Initialization delay(1) ACMD 41 ACMD 41 CMD2 NCC NCC NCC Optional repetitions of ACMD41, until no card responds with the busy bit set. Time out value for initialization process(2) Supply voltage time |
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