Renesas RX Series User Manual

R01UH0823EJ0100 Rev.1.00 Page 1448 of 1823
Jul 31, 2019
RX23W Group 40. SD Host Interface (SDHIa)
40.3.2 SD Buffer and the SDBUFR Register
The SDHI transfers data to an SD card via its internal SD buffer. The SD buffer is comprised of a double buffer, and each
buffer is 512 bytes.
Figure 40.4 shows the data configuration of a single buffer of the SD buffer’s double buffer.
Figure 40.4 Data Configuration of Single Buffer in the SD Buffer
Access to the SD buffer is done via the SDBUFR register. If data is written to the SDBUFR register while the
SDSWAP.BWSWP bit is 1, the SDHI swaps the endian for the byte, and stores the data in the SDBUFR register. If data
is read from the SDBUFR register while the SDSWAP.BRSWP bit is 1, the data of the endian for the byte that was
swapped can be read.
Figure 40.5 shows the data alignment when reading the SDBUFR register.
Figure 40.5 Data Alignment When Reading the SDBUFR Register
Word
MSB LSB
0
30 29 28 27 26 25 24 23 16
Byte 2
15 8
Byte 1 Byte 0
7 6 5 4 3 2 1 0
Byte 3
31
1
30 29 28 27 26 25 24 23 16
Byte 6
15 8
Byte 5 Byte 4
7 6 5 4 3 2 1 0
Byte 7
31
127
30 29 28 27 26 25 24 23 16
Byte 510
15 8
Byte 509 Byte 508
7 6 5 4 3 2 1 0
Byte 511
31
When bytes are not swapped (SDSWAP.BRSWP bit is 0)
SDBUFR register 23 16
Byte (4
n + 2)
15 8
Byte (4
n)
7 6 5 4 3 2 1 0
Byte (4
n + 3)
30 29 28 27 26 25 2431
Byte (4
n + 1)
When bytes are swapped (SDSWAP.BRSWP bit is 1)
SDBUFR register 15 8
Byte (4
n + 1)
23 16
Byte (4
n + 3)
31 30 29 28 27 26 25 24
Byte (4
n)
6 5 4 3 2 1 07
Byte (4
n + 2)
In this diagram,
n = 0 to 127.

Renesas RX Series Specifications

General

Brand	Renesas
Model	RX Series
Category	Microcontrollers
Language	English