140
4.5.5
Pins Used for DRAM Interface
Table 4.7 shows the pins used for DRAM interfacing and their functions.
Table 4.7
DRAM Interface Pins
Pin
With DRAM
Setting
Name
I/O
Function
HWR
WE
Write enable
Output
Write enable for DRAM space
access
CS2
RAS2
Row address strobe 2
Output
Row address strobe when area 2
is designated as DRAM space
Row address strobe when areas
2 to 5 are designated as
continuous DRAM space
CS3
RAS3
Row address strobe 3
Output
Row address strobe when area 3
is designated as DRAM space
CS4
RAS4
Row address strobe 4
Output
Row address strobe when area 4
is designated as DRAM space
CS5
RAS5
Row address strobe 5
Output
Row address strobe when area 5
is designated as DRAM space
UCAS
UCAS
Upper column address
strobe
Output
Upper column address strobe for
16-bit DRAM space access
Column address strobe for 8-bit
DRAM space access
LCAS
LCAS
Lower column address
strobe
Output
Lower column address strobe
signal for 16-bit DRAM space
access
RD
,
OE
OE
Output enable
Output
Output enable signal for DRAM
space access
WAIT
WAIT
Wait
Input
Wait request signal
A15 to A0
A15 to A0
Address pins
Output
Row address/column address
multiplexed output
D15 to D0
D15 to D0
Data pins
I/O
Data input/output pins
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