SH7710 Datasheet, PDF (460/996 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7700 Series

Section 12 Bus State Controller (BSC)
Burst Write: A burst write occurs in the following cases in this LSI.
1. Access size in writing is larger than data bus width.
2. Copyback of the cache
3. 16-byte transfer in DMAC or E-DMAC (access to non-cachable region)
This LSI always accesses SDRAM with burst length 1. For example, write access of burst length 1
is performed continuously 4 times to write 16-byte continuous data to the SDRAM that is
connected to a 32-bit data bus. The relationship between the access size and the number of bursts
is shown in table 12.18.
Figure 12.17 shows a timing chart for burst writes. In burst write, an ACTV command is output in
the Tr cycle, the WRIT command is issued in the Tc1, Tc2, and Tc3 cycles, and the WRITA
command is issued to execute an auto-precharge in the Tc4 cycle. In the write cycle, the write data
is output simultaneously with the write command. After the write command with the auto-
precharge is output, the Trw1 cycle that waits for the auto-precharge initiation is followed by the
Tap cycle that waits for completion of the auto-precharge induced by the WRITA command in the
SDRAM. In the Tap cycle, a new command will not be issued to the same bank. However, access
to another CS space or another bank in the same SDRAM space is enabled. The number of Trw1
cycles is specified by the TRWL1 and TRWL0 bits in CS3WCR. The number of Tap cycles is
specified by the TRP1 and TRP0 bits in CS3WCR.
Rev. 2.00 Dec. 07, 2005 Page 418 of 950
REJ09B0079-0200