Renesas SH7781 - Manual (Page 457)

11. Local Bus State Controller (LBSC)
Rev.1.00 Jan. 10, 2008 Page 427 of 1658
REJ09B0261-0100
11.5.6 MPX Interface
When both the MODE 7 pin is set to 0 at a power-on reset by the
PRESET pin, the MPX interface
is selected for area 0. The MPX interface is selected for areas 1 to 6 by the MPX bit in CS1BCR,
CS2BCR, and CS4BCR to CS6BCR. The MPX interface provides an address/data multiplex-type
bus protocol and facilitates connection with external memory controller chips using an
address/data multiplex-type 64- or 32-bit single bus. A bus cycle consists of an address phase and
a data phase. In the address phase, address information is output on D25 to D0, and the access size
is output on D63 to D61 for the 64-bit bus and on D31 to D29 for the 32-bit bus. The
BS signal is
asserted for one cycle to indicate the address phase. The
CSn signal is asserted at the rising edge in
Tm1 and is negated after the end of the last data transfer in the data phase. Therefore, a negation
cycle is not generated in the case of minimum pitch access. The
FRAME signal is asserted at the
rising edge in Tm1 and negated at the start of the last data transfer cycle in the data phase.
Therefore, an external device for the MPX interface must internally store the address information
and access size output in the address phase and perform data input/output for the data phase. For
details, see section 11.5.1, Endian/Access Size and Data Alignment.
Values output to address pins A25 to A0 are not guaranteed.
In 32-byte transfer, a total of 32 bytes are transferred continuously according to the set bus width.
The first access is performed on the data for which an access request is issued, and the remaining
accesses are performed according to the set bus width. If the access size is larger than the bus
width, a burst access with continuing multiple data cycles occurs after one address output. The bus
is not released during this transfer.
Table 11.17 Relationship between D63/D31 to D61/D29 and Access Size in Address Phase
D63/D31 D62/D30 D61/D29 Access Size
0 0 0 Byte
1 Word
1 0 Longword
1 Unused
1 X X 32-byte burst
Legend:
X: Don't care