MC2GH256NMCA-2SA00 SAMSUNG [Samsung semiconductor], MC2GH256NMCA-2SA00 Datasheet - Page 79

• Manufacturer Part Number: MC2GH256NMCA-2SA00
• Description: SAMSUNG MultiMediaCard
• Manufacturer: SAMSUNG [Samsung semiconductor]

The SPI mode consists of a secondary, optional communication protocol which is offered by Flash-based MultiMedi-
aCards. This mode is a subset of the MultiMediaCard protocol, designed to communicate with a SPI channel, commonly
found in Motorola’s (and lately a few other vendors’) microcontrollers. The interface is selected during the first reset com-
mand 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 SPI
implementation uses a subset of the MultiMediaCard protocol and command set. It is intended to be used by systems
which typically require one card and have lower data transfer rates (compared to MultiMediaCard protocol based sys-
tems). 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 minimum. The disadvantage is the loss of performance of the SPI mode versus Mul-
tiMediaCard mode (lower data transfer rate, hardware CS, etc.).
The Serial Peripheral Interface (SPI) is a general purpose synchronous serial interface originally found on certain Motorola
microcontrollers. A virtually identical interface can now be found on certain TI and SGS Thomson 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.
Another SPI common characteristic is byte transfers, which is implemented in the card as well. All data tokens are multi-
ples of bytes (8 bit) and always byte aligned to the CS signal.
The card identification and addressing methods are replaced by a hardware Chip Select (CS) signal. There are no broad-
cast commands. For every command, a card (slave) is selected by asserting (active low) the CS signal (see 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 program-
ming process.
The bidirectional CMD and DAT lines are replaced by unidirectional dataIn and dataOut signals.
The MultiMediaCard pin assignment in SPI mode (compared to MultiMediaCard mode) is given in Table 7-1.
Introduction
7.1 SPI Interface Concept
7.2 SPI Bus Topology
Revision 0.3
7. SPI Mode
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MultiMediaCard
Sep.22.2005
TM