CHAPTER 6 BUS CONTROL
User’s Manual U14272EJ3V0UM
136
6.5.4 SDTIMINGREG (0x0A00 030C)
Bit
15
14
13
12
11
10
9
8
Name
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
Reserved
R/W
R
R
R
R
R
R
R/W
R/W
At reset
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
Name
TRAS1
TRAS0
TRC1
TRC0
TRP1
TRP0
TRCD1
TRCD0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
At reset
0
0
0
0
0
0
0
0
Bit
Name
Function
15 to 10
Reserved
0 is returned when read
9
Reserved
Write 0 when write.
Note
8
Reserved
Write 1 when write.
Note
7, 6
TRAS(1:0)
TRAS in clock cycles
00 : 3 SDCLK (for 25 MHz SDCLK)
01 : 5 SDCLK (for 66, 50, or 33 MHz SDCLK)
Others : Prohibited
5, 4
TRC(1:0)
TRC in clock cycles
00 : 4 SDCLK (for 25 MHz SDCLK)
01 : 7 SDCLK (for 66, 50, or 33 MHz SDCLK)
Others : Prohibited
3, 2
TRP(1:0)
TRP in clock cycles
00 : 1 SDCLK (for 25 MHz SDCLK)
01 : Prohibited
10 : 3 SDCLK (for 66, 50, or 33 MHz SDCLK)
11 : Prohibited
1, 0
TRCD(1:0)
TRCD in clock cycles
00 : 1 SDCLK (for 25 MHz SDCLK)
01 : 2 SDCLK (for 66, 50, or 33 MHz SDCLK)
Others : Prohibited
Note Bits 9 and 8 must be set to 01 before using SDRAM. Especially, be sure to set 1 to bit 8 since its default value
is 0. When these bits are not 01, the V
R
4181 may not work correctly.
This register is used to set SDRAM timing parameters. Software must set this register suitable before using
SDRAM.