SH7751 Group, SH7751R Group
Section 13 Bus State Controller (BSC)
R01UH0457EJ0301 Rev. 3.01
Page 429 of 1128
Sep 24, 2013
Address Multiplexing:
Synchronous DRAM can be connected without external multiplexing
circuitry in accordance with the address multiplex specification bits AMXEXT and AMX2–
AMX0 in MCR. Table 13.15 shows the relationship between the address multiplex specification
bits and the bits output at the address pins. See Appendix E, Synchronous DRAM Address
Multiplexing Tables.
The address signals output at address pins A25–A18, A1, and A0 are not guaranteed.
When A0, the LSB of the synchronous DRAM address, is connected to this LSI, it makes a
longword address specification. Connection should therefore be made in this order: connect pin
A0 of the synchronous DRAM to pin A2 of this LSI, then connect pin A1 to pin A3.
Table 13.15 Example of Correspondence between LSI and Synchronous DRAM Address
Pins (32-Bit Bus Width, AMX2–AMX0 = 000, AMXEXT = 0)
LSI Address Pin
Synchronous DRAM Address Pin
RAS
Cycle
CAS Cycle
Function
A13
A21
A21
A11
BANK select bank address
A12
A20
H/L
A10
Address precharge setting
A11 A19
0 A9
Address
A10 A18
0 A8
A9 A17
A9
A7
A8 A16
A8
A6
A7 A15
A7
A5
A6 A14
A6
A4
A5 A13
A5
A3
A4 A12
A4
A2
A3 A11
A3
A1
A2 A10
A2
A0
A1
Not used
Not used
Not used
A0
Not used
Not used
Not used
Burst Read:
The timing chart for a burst read is shown in figure 13.24. In the following example
it is assumed that two 512k
×
16-bit
×
2-bank synchronous DRAMs are connected, and a 32-bit
data width is used. The burst length is 4. After the Tr cycle in which the ACTV command is
output, a READ command is issued in the Tc1 cycle and, 4 cycles after that, a READA command
is issued and read data is fetched on the rising edge of the external command clock (CKIO) from
cycle Td1 to cycle Td8. The Tpc cycle is used to wait for completion of auto-precharge based on