H8S2456 Datasheet, PDF (290/1376 Pages) Renesas Technology Corp – 16-Bit Single-Chip Microcomputer H8S Family / H8S/2400 Series

Section 6 Bus Controller (BSC)
6.8.12 Burst Operation
With synchronous DRAM, in addition to full access (normal access) in which data is accessed by
outputting a row address for each access, burst access is also provided which can be used when
making consecutive accesses to the same row address. This access enables fast access of data by
simply changing the column address after the row address has been output. Burst access can be
selected by setting the BE bit to 1 in DRAMCR.
DQM has the 2-cycle latency when synchronous DRAM is read. Therefore, the DQM signal
cannot be specified to the Tc2 cycle data output if the Tc1 cycle is executed for second or
following column address when the CAS latency is set to 1 to issue the READ command. Do not
set the BE bit to 1 when synchronous DRAM of CAS latency 1 is connected.
(1) Burst Access Operation Timing
Figure 6.64 shows the operation timing for burst access. When there are consecutive access cycles
for continuous synchronous DRAM space, the column address output cycles continue as long as
the row address is the same for consecutive access cycles. The row address used for the
comparison is set with bits MXC2 to MXC0 in DRAMCR.
Rev. 1.00 Sep. 19, 2008 Page 260 of 1342
REJ09B0467-0100