Specifications

©Copyright 2001-2013 SD Group (Panasonic, SanDisk, Toshiba) and SD Card Association
Physical Layer Simplified Specification Version 4.10
129
5.7 Function Extension Specification
There are demands for adding extension functions in the SD Memory Card. With regard to CMD6, it is
not suitable for active control but suitable for selecting one of functions at initialization. Then new
function extension method suitable for active control is introduced.
Extension Register is introduced to control extension functions. The Extension Register space is
independent to Memory Space accessed by CMD17/18 and CMD24/25. Commands CMD48/49 and
CMD58/59 are defined to access Extension Register Space.
CMD48: Read Extension Register Single Block Command
CMD49: Write Extension Register Single Block Command
CMD58: Read Extension Register Multi-Block Command
CMD59: Write Extension Register Multi-Block Command
There are two types of Extension Register Spaces; Memory Extension Register Space and I/O
Extension Register Space. I/O Extension Register Space is equivalent to the space accessed by
CMD52 and CMD53 as defined by the SDIO Specification.
As most host systems can perform 512byte block basis read/write operation, CMD48/49 are defined as
512 bytes fixed block length commands. "Data Port" can be defined in the Extension Register space to
perform data transfer between host and a function device. Location of Data Port is defined by each
function specification. CMD49 has specific features to perform bit operation without "Read Modify
Write". Multiple blocks data transfer is supported by CMD58/59 to increase performance.
This function extension method also defines "General Information" to realize Plug & Play in a host
system. General Information includes information to find function driver.
Host shall set reserved bits in a defined writable Extension Register to 0. Even if reserved bits were set
to 1, Device is not necessary to set reserved bits to 1.
Function Extension Specification is newly added to the Physical Layer Version 4.00 and is applicable
from the Physical Version 4.00 products. This function may be supported on SDHC and SDXC Card
and is not supported through SPI interface. From the Physical Layer Version 4.10, Multi-Block
commands are supported.
5.7.1 Extension Register Space
Figure 5-3 shows Extension Register Space. The space is divided into 256 pages per a Function
Number. Each page is 512 byte length of fixed address boundary. Function Number is 1 to 15 in case of
Memory Space and 1 to 7 in case of I/O Space. CMD48/49 cannot access data across page boundary.
Embodiment of Extension Register Set is defined anywhere in the Extension Register Space by a
Function Specification. Extension Register Set should be treated as a different type of register from that
shown in Table 3-2.
Figure 5-3 : Extension Register Space
A Page of
Extension
Register
Space
512-byte
Extension Register Space consists
of 256 pages per function.