10 SDRAM CONTROLLER (SDRAMC)
10-20
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
SDRAM Application Configuration Register (SDRAMC_APP)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
SDRAM
Application
Configuration
Register
(SDRAMC_APP)
0x302210
(32 bits)
D31–6 –
reserved
–
–
–
0 when being read.
D5
DBF
Double frequency mode enable
1 Enable
0 Disable
0
W
D4
–
reserved
–
–
–
D3–2 CAS[1:0]
CAS latency setup
CAS[1:0]
CAS latency
0x2 R/W
0x3
0x2
0x1
0x0
3
2
1
reserved
D1
–
reserved
–
–
–
0 when being read.
D0
–
reserved
–
0
R/W Do not set to 1.
D[31:6] Reserved
D5
DBF: Double Frequency Mode Enable Bit
Enables double frequency mode.
1 (R/W): Enabled
0 (R/W): Disabled (default)
Setting DBF to 1 sets the SDRAMC to operate in the double frequency mode where it can use the
SDRAM clock (72 MHz max.) that is two times faster than the CPU clock (36 MHz max.). Set DBF to
0 to use the SDRAM clock at the same frequency as the CPU clock (60 MHz max.).
D4
Reserved
D[3:2]
CAS[1:0]: CAS Latency Setup Bits
Sets the CAS latency.
CAS latency refers to the number of SDCLK clock cycles counted until data is output from the
SDRAM after issuing the READ command.
7.7 CAS Latency Settings
Table 10.
CAS[1:0]
CAS latency
0x3
3
0x2
2
0x1
1
0x0
Reserved
(Default: 0x2)
D1
Reserved
D0
Reserved (Always set this bit to 0.)
Precautions
10.8
If the operating clock (SDCLK) is stopped while the SDRAM is being accessed, a system failure may occur due to
stoppage of the SDRAM operation in uncontrolled status. The following operations stop the SDCLK. Do not per-
form these operations when the SDRAM may be accessed.
- Placing the S1C33L26 into SLEEP status
- Disabling the clock supply to the SDRAMC module
Besides from the CPU, the SDRAM can be accessed from the DMAC (if DMA transfers are enabled toward
the SDRAM). In this case, before performing the above operations, stop the DMAC to disable its access to the
SDRAM.