Datasheet

195
10.4.4 Burst Operation
High-Speed Page Mode: When the burst enable bit (BE) of the DCR is set, burst accesses can be
performed using high speed page mode. The timing is shown in figure 10.12. Wait cycles can be
inserted during burst accesses by using the DCR.
T
p
T
c1
T
c2
T
c1
T
c2
T
r
CK
Write
Read
Address
Data
RAS
CASx
RDWR
Data
RDWR
CASx
RAS
Row Column Column
Figure 10.12 DRAM Bus Cycle (High-Speed Page Mode)
RAS Down Mode: There are some instances where even if burst operation is selected, continuous
accesses to DRAM will not occur, but another space will be accessed instead part way through the
access. In such cases, if the RAS signal is maintained at low level during the time the other space
is accessed, it is possible to continue burst operation at the time the next DRAM same row address
is accessed. This is called RAS down mode.
To use RAS down mode, set both the BE and RASD bits of the DCR to 1.
Figures 10.13 and 10.14 show operation in RAS up and down modes.