125
4.8 Area Mode Register 4 (AMD4)
4.8
Area Mode Register 4 (AMD4)
Area mode register 4 (AMD4) specifies the operation mode of chip select area 4 (area
specified by ASR4 and AMR4).
Area 4 allows the use of the DRAM interface.
■
Configuration of Area Mode Register 4 (AMD4)
Area mode register 4 (AMD4) is configured as follows:
■
Bit Functions of Area Mode Register 4 (AMD4)
[bit 7] DRME (DRaM Enable bit)
The DRME bit selects the usual bus interface or DRAM interface for area 4.
0: Usual bus interface
1: DRAM interface
When the DRAM interface is used, more details must be specified via the DMCR (DRAM
control register), which is described later.
[bit 4 and 3] BW1 and 0 (Bus Width bit)
BW1 and BW0 specify the bus width of area 4. These bits have functions similar to those of
the BW bits of other AMD registers. When the DRAM interface is used, the bus width
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 automatically inserted when area 4
is accessed via memory.
These bits have functions similar to those of the WTC bits of other AMD registers. By
resetting the bits to "000", the number of wait cycles to be inserted automatically becomes
"0".
When the DRAM interface is used because wait cycles are controlled by the DMCR, WTC2
to WTC0 become invalid.
7
6
5
4
3
2
1
0
AMD4
0623
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
Содержание MB91F109
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Страница 95: ...71 2 10 Operation Mode MODR writing RSTX reset MD2 1 0 BW1 and BW0 of AMD0 to AMD5 Bus width specification ...
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Страница 314: ...290 CHAPTER 12 16 BIT RELOAD TIMER ...
Страница 322: ...298 CHAPTER 13 BIT SEARCH MODULE ...
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Страница 449: ...425 INDEX INDEX The index follows on the next page This is listed in alphabetic order ...
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