MultiMediaCardTM
4.5 Registers
Table 4-3 MultiMediaCard Information Registers
Name
OCR
Width
32
Type
Programmed by the
manufacturer. Read only for
user
Description
Supported voltage range, card power
up status bit
CID
128
16
Programmed by the
manufacturer. Read only for
user
Programmed during
initialization, not readable
Card identification number, card
individual number for identification.
RCA
Relative card address, local system
address of a card, dynamically
assigned by the host during
initialization.
CSD
128
Programmed by the
manufacturer. Partially
Programmable by the user
Card specific data, information about
the card operation conditions.
CID and RCA are used for identifying and addressing MultiMediaCard. CSD contains the card specific
data record. This record is a set of information fields to define the operation conditions of the
MultiMediaCard.
For the user the CID and the OCR are read only registers. They are read out by special commands
(refer to Chapter “Commands”). The RCA registers are write only registers. Unlike CID and CSD, RCA
looses its contents after powering down the card. Its value is reassigned in each initialization cycle.
The MultiMediaCard registers usage in SPI mode is summarized in Table “MultiMediaCard Registers in
SPI Mode
Table 4-4 Information Registers in SPI Mode
Name Width (bytes)
Available
Yes
Description
Operation condition register
Card identification data (serial number,
manufacturer ID etc.)
OCR
CID
4
16
Yes
RCA
CSD
No
Yes
16
Card specific data, information about the card
operation conditions
4.5.1 Operation Condition Register (OCR)
This register indicates supported voltage range of MultiMediaCards. It is a 32 bit wide register and for
read only.
Table 4-5 OCR Fields
20
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