HD6413007F20 Datasheet, PDF (177/798 Pages) Renesas Technology Corp – Hardware Manual Renesas 16-Bit Single-Chip Microcomputer H8 Family/H8/300H Series

6. Bus Controller
6.5 DRAM Interface
6.5.1 Overview
The H8/3006 and H8/3007 are provided with a DRAM interface with functions for DRAM control
signal (RAS, UCAS, LCAS, WE) output, address multiplexing, and refreshing, that direct
connection of DRAM. In the expanded modes, external address space areas 2 to 5 can be
designated as DRAM space accessed via the DRAM interface. A data bus width of 8 or 16 bits can
be selected for DRAM space by means of a setting in ABWCR. When a 16-bit data bus width is
selected, CAS is used for byte access control. In the case of × 16-bit organization DRAM,
therefore, the 2-CAS type can be connected. A fast page mode is supported in addition to the
normal read and write access modes.
6.5.2 DRAM Space and RAS Output Pin Settings
Designation of areas 2 to 5 as DRAM space, and selection of the RAS output pin for each area
designated as DRAM space, is performed by setting bits DRAS2 to DRAS0 in DRCRA. Table 6.5
shows the correspondence between the settings of bits DRAS2 to DRAS0 and the selected DRAM
space and RAS output pin.
When an arbitrary value has been set in DRAS2 to DRAS0, a write of a different value other than
000 must not be performed.
Table 6.5 Settings of Bits DRAS2 to DRAS0 and Corresponding DRAM Space
(RAS Output Pin)
DRAS2 DRAS1 DRAS0 Area 5
Area 4
Area 3
Area 2
0
0
0
Normal space Normal space Normal space Normal space
1
Note:
1
Normal space Normal space Normal space DRAM space
(CS₂)
1
0
Normal space Normal space DRAM space DRAM space
(CS₃)
(CS₂)
1
Normal space Normal space
DRAM space (CS₂)*
0
0
Normal space DRAM space DRAM space DRAM space
(CS₄)
(CS₃)
(CS₂)
1
DRAM space DRAM space DRAM space DRAM space
(CS₅)
(CS₄)
(CS₃)
(CS₂)
1
0
DRAM space (CS₄)*
DRAM space (CS₂)*
1
DRAM space (CS₂)*
*
A
single
CS
n
pin
serves
as
a
common
RAS
output
pin
for
a
number
of
areas.
Unused
CS
n
pins
can
be
used
as
input/output
ports.
Rev.5.00 Sep. 12, 2007 Page 147 of 764
REJ09B0396-0500