SDMJ-32 SanDisk, SDMJ-32 Datasheet - Page 66

• Manufacturer Part Number: SDMJ-32
• Manufacturer: SanDisk
• Type: MultiMedia Cardr

Specifications of SDMJ-32

• Density: 32MByte
• Operating Supply Voltage (typ): 3.3V
• Operating Temperature (min): -25C
• Operating Temperature (max): 85C
• Package Type: MMC
• Mounting: Socket
• Pin Count: 7
• Operating Temperature Classification: Commercial
• Operating Supply Voltage (min): 2.7V
• Operating Supply Voltage (max): 3.6V
• Programmable: Yes
• Lead Free Status / RoHS Status: Compliant

Revision 1.3
© 2005 SanDisk Corporation
5.1
5.2
5
SPI Interface Concept
SPI Bus Topology
SPI Mode
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 MultiMediaCard/RS-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.).
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:
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.
Card identification and addressing methods are replaced by the hardware Chip Select (CS)
signal; there are no broadcast commands. For every command, a card (slave) is selected by
asserting (active low) the CS signal. See the following figure.
The CS signal must be continuously active for the duration of the SPI transaction
(command, response and data). The only exception occurs during card programming when
the host can de-assert the CS signal without affecting the programming process.
The bi-directional CMD and DAT lines are replaced by unidirectional dataIn and dataOut
signals. This eliminates the ability to execute commands while data is being read or written
and, therefore, makes the sequential and multi block read/write operations obsolete. The
SPI channel supports single block read/write commands only.
The SPI interface uses the same seven signals as the standard MultiMediaCard bus (Figure
5-1).
SPI mode is a secondary, optional communication protocol, which is offered by the
•
•
•
•
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
5-1
MultiMediaCard/RS-MultiMediaCard Product Manual
Chapter 5 –SPI Mode
04/21/05