Specifications

©Copyright 2001-2013 SD Group (Panasonic, SanDisk, Toshiba) and SD Card Association
Physical Layer Simplified Specification Version 4.10
109
The line B illustrated in Figure 4-57 shows another example of erase characteristics. The red line
indicates the erase timeout value that the host should use. Since the time-out is bigger than 1 second,
the red line and line B are equivalent.
Erase time of an AU shall be less than 3 second. T
OFFSET
is mainly used to adjust erase timeout of an
AU.
Figure 4-57: Example Erase Characteristics (Case 2 TOFFSET=2)
4.14.3 Method for Erase Large Areas
The calculated erase timeout for multiple AUs might be too large compared with the actual erase time.
The calculation of erase timeout is not accurate because calculated timeout includes a margin. A
margin per AU accumulates and the result of calculating the timeout for large number of AUs will
include large margins. Such calculations would be meaningless because the range of margin might be
in order of minutes. Therefore, a small number of AUs should be erased at one time. This enables the
host to calculate smaller timeout with fewer errors.
Application Note:
When a large area is erased, the host should divide
it into small areas at the AU boundary and
continuously erase the small areas using a small area erase timeout. It may take a long time to erase a
large area, so the host should inform the user about the erase progress, otherwise the user might abort
the execution of the erase.
4.14.4 Calculation of Erase Timeout Value Using the Parameter Registers
Erase Timeout of X AU can be calculated by Equation (6).
Erase Time-out of X AU
OFFSET
ERASE
ERASE
TX
N
T
+⋅
=
...........................................(6)
Erase timeout is determined by following steps:
(1) Calculate Equation (6).
(2) If the result of (1) is less than 1 second, the timeout is set to 1 second.
(3) 250 ms should be added to the result of (2) for each partial erase AU. When the start and end
blocks are in partially erase AUs, add 500 ms to the result of (2).
0
1 2
Number of AU Erased
Erase Timeout [Sec]
N
ERASE
1
2
3
Line B
T
OFFSET
3
T
ERASE