Renesas H8SX/1650, Руководство по оборудованию

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Section 6 Bus Controller (BSC)
Rev.2.00 Jun. 28, 2007 Page 179 of 666
REJ09B0311-0200
6.7 Byte Control SRAM Interface
The byte control SRAM interface is a memory interface for outputting a byte select strobe during
a read or a write bus cycle. This interface has 16-bit data input/output pins and can be connected to
the SRAM that has the upper byte select and the lower byte select strobes such as
UB
and
LB
.
The operation of the byte control SRAM interface is the same as the basic bus interface except
that: the byte select strobes (
LUB
and
LLB
) are output from the write strobe output pins (
LHWR
and
LLWR
), respectively; the read strobe (
RD
) negation timing is a half cycle earlier than that in
the case where RDNn = 0 in the basic bus interface regardless of the RDNCR settings; and the
RD/
WR
signal is used as write enable (
WE
).
6.7.1 Byte Control SRAM Space Setting
Byte control SRAM interface can be specified for areas 0 to 7. Each area can be specified as byte
control SRAM interface by setting bits BCSELn (n = 0 to 7) in SRAMCR. For the area specified
as burst ROM interface or address/data multiplexed I/O interface, the SRAMCR setting is invalid
and byte control SRAM interface cannot be used.
6.7.2 Data Bus
The bus width of the byte control SRAM space can be specified as 16-bit byte control SRAM
space according to bits ABWHn and ABWLn (n = 0 to 7) in ABWCR. The area specified as 8-bit
access space cannot be specified as the byte control SRAM space.
For the 16-bit byte control SRAM space, data bus (D15 to D0) is valid.
Access size and data alignment are the same as the basic bus interface. For details, see section
6.5.6, Endian and Data Alignment.