Revision 1.0 MultiMediaCardRS-MultiMediaCard Product Manual
© 2004 SanDisk Corporation 4-27
051304
4.11 Timing Values
Table 4-12 defines all timing values.
Table 4-12 Timing Values
Value Min. Max. Unit
N
CR
2 64
Clock cycles
N
ID
5 5
Clock cycles
N
AC
2 Note
Clock cycles
N
RC
8 ---
Clock cycles
N
CC
8 ---
Clock cycles
N
WR
2 ---
Clock cycles
NOTE: 10 TAACf + 100NSAC] where f is the clock frequency.
Revision 1.0 MultiMediaCardRS-MultiMediaCard Product Manual
© 2004 SanDisk Corporation 5-1
051304
5 SPI Mode
SPI mode is a secondary, optional communication protocol, which is offered by the MultiMediaCard and RS-MultiMediaCard. This mode is a subset of the MultiMediaCard
Protocol, designed to communicate with an SPI channel, commonly found in some vendors’ microcontrollers. The interface is selected during the first reset command after
power up CMD0 and cannot be changed once the part is powered on.
The SPI standard defines the physical link only, and not the complete data transfer protocol. The MultiMediaCardRS-MultiMediaCard SPI implementation uses a subset of
the MultiMediaCard Protocol and command set because it pertains to systems that require a small number of cards typically one and have lower data transfer rates compared to
MultiMediaCard Protocol-based systems. From the application point of view, the advantage of the SPI mode is the capability of using an off-the-shelf host, hence reducing
the design-in effort to a minimum. The disadvantage is the loss of performance with SPI mode as compared to MultiMediaCard mode lower data transfer rate, fewer cards,
hardware CS per card, etc..
5.1 SPI Interface Concept
The SPI is a general purpose synchronous serial interface originally found on certain Motorola microcontrollers. A virtually identical interface can now be found on some other
microcontrollers as well.
The MultiMediaCard SPI interface is compatible with SPI hosts available on the market. As in any other SPI device, the MultiMediaCard SPI channel consists of the following four
signals: •
CS—Host to card Chip Select signal •
CLK—Host to card clock signal •
DataIn—Host to card data signal •
DataOut—Card to host data signal Byte transfers are another common SPI characteristic. They are implemented in the card as
well. All data tokens are multiples of bytes 8-bit and always byte aligned to the CS signal.
5.2 SPI Bus Topology
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