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CHAPTER 4 BUS INTERFACE
4.9 Area Mode Register 5 (AMD5)

Area mode register 5 (AMD5) specifies the bus mode of chip select area 5 (area

specified by ASR5 and AMR5).

Area 5 allows the use of the DRAM interface.

■Configuration of Area Mode Register 5 (AMD5)
Area mode register 5 (AMD5) is configured as follows:
■Bit Functions of Area Mode Register 5 (AMD5)
[bit 7] DRME (DRaM Enable bit)
The DRME bit selects the usual bus interface or DRAM interface for area 5.
0: Usual bus interface
1: DRAM interface
When the DRAM interface is used, more details must be specified via the DMCR (DRA M
control register) described later.
[bit 4 and 3] BW1 and 0 (Bus Width bit)
BW1 and BW0 specify the bus width of area 5. These bits have functions similar to those of
the BW bits of other AMD registers. When the DRAM interface is used, the bus wi dth
specified by these bits is also valid.
[bit 2 to 0] WTC 2 to 0 (Wait Cycle bit)
WTC2 to WTC0 specify the number of wait cycles to be automatical ly inserted when a rea 5
is accessed via memory.
These bits have functions similar to those of the WTC bits of other AMD registers. By
resetting these bits to "000", the number of wait cycles to be automa tical ly inse rted b ecomes
"0".
When the DRAM interface is used because wait cycles are controlled b y the DMCR, WTC2
to WTC0 become invalid.
76543210

AMD5 0624

H

DRME BW1 BW0 WTC2 WTC1 WTC0 0--00000 R/W

Address: 0000

Initial value Access

BW1 BW0 Bus width
0
0
1
1
0
1
0
1
8 bits
16 bits
Setting disabled
Reserved