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Programmer’s Reference
Copyright © ARM Limited 2000. All rights reserved.
4-31
4.6
MMC programming
The SPI bus is used to provide the interface between the SA-1100 and MMC interface
(see SPI bus on page 3-29).
This section provides an overview of how the MMC SPI interface operates. However,
because different card types have different timing requirements, you are advised to
consult the documentation supplied by the MultiMediaCard manufacturer for more
specific information.
4.6.1
MMC/SPI bus protocol
As well as flash memory or ROM (depending upon card type), MMCs incorporate an
intelligent interface controller. Data transfers are handled using a message-based
protocol. The SPI implementation uses a subset of the MMC protocol.
Three types of messages are used:
command
these are always 6 bytes in length, as shown in Figure 4-9, and
include a 7-bit CRC checksum. The checksum is ignored in SPI
mode. Commands are transferred serially on the CPU_SPI_TXD
signal.
response
responses are replies by the card to a previously received
command. These are transferred on the CPU_SPI_RXD signal.
data
data is transferred on the CPU_SPI_RXD when read from the
card or CPU_SPI_TXD when written to the card. Data transfers
always use multiples of 8 bits on the SPI bus which are byte
aligned to the chip select signal
Figure 4-9 MMC command token
Content
CRC
0
0
1
2
48
47
40
39
1
0
Summary of Contents for Prospector P1100
Page 1: ...ARM DUI 0122A Prospector P1100 User Guide ...
Page 4: ...iv Copyright ARM Limited 2000 All rights reserved ARM DUI 0122A ...
Page 86: ...Hardware Description 3 54 Copyright ARM Limited 2000 All rights reserved ARM DUI 0122A ...
Page 140: ...Connector reference A 18 Copyright ARM Limited 2000 All rights reserved ARM DUI 0122A ...