SH7619_09 Datasheet, PDF (183/860 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7619 Series

Section 7 Bus State Controller (BSC)
7.5 Operation
7.5.1 Endian/Access Size and Data Alignment
This LSI supports big endian, in which the most significant byte (MSByte) of multiple byte data is
stored in the lower address, and little endian, in which the least significant byte (LSByte) of
multiple byte data is stored in the lower address. Endian is specified at a power-on reset by the
external pin (MD5). When pin MD5 is driven low at a power-on reset, the endian will become big
endian and when pin MD5 is driven high at a power-on reset, the endian will become little endian.
Three data bus widths (8, 16, and 32 bits) are available for normal memory and byte-selection
SRAM. Two data bus widths (16 and 32 bits) are available for SDRAM. Two data bus widths (8
and 16 bits) are available for PCMCIA interface. Data alignment is performed in accordance with
the data bus width of the device and endian. This also means that when longword data is read from
a byte-width device, the read operation must be done four times. In this LSI, data alignment and
conversion of data length is performed automatically between the respective interfaces.
Tables 7.6 to 7.11 show the relationship between endian, device data width, and access unit.
Table 7.6 32-Bit External Device/Big Endian Access and Data Alignment
Data Bus
Strobe Signals
Operation
WE3(BE3), WE2(BE2), WE1(BE1), WE0(BE0),
D31 to D24 D23 to D16 D15 to D8 D7 to D0 DQMUU DQMUL DQMLU DQMLL
Byte access at 0
Data



Assert 


7 to 0
Byte access at 1

Data



Assert 

7 to 0
Byte access at 2


Data



Assert 
7 to 0
Byte access at 3



Data



Assert
7 to 0
Word access at 0
Data
Data


Assert Assert 

15 to 8 7 to 0
Word access at 2


Data
Data


Assert Assert
15 to 8 7 to 0
Longword access at 0 Data
Data
Data
Data
31 to 24 23 to 16 15 to 8 7 to 0
Assert Assert Assert Assert
Rev. 6.00 Jul. 15, 2009 Page 143 of 816
REJ09B0237-0600