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Functional Overview
2.3.3 External SDRAM
Rev.1.00 June 1,2005 2-7
REJ11J0002-0100Z
2
Table2.3.4 lists bus state controller settings for operation with the SH7206 Bus clock at 66.67MHz.
Table2.3.4 Examples for Bus State Controller Settings (SDRAM Read/ Write)
User Area Application Device Bus State Controller Settings
CS3 EDS1216AATA-75E
CS3 Space Bus Control Register (CS3BCR)
Initial value: H'36DB 0600
Recommended set value: H'0000 4400 (for 16-bit bus) or H'0000 4600
(for 32-bit bus)
• Specify memory
TYPE[2:0] B'100; SDRAM
• Specify data bus
BSZ[1:0] = B'10; 16-bit bus width
BSZ[1:0] = B'11; 32-bit bus width
CS3 Space Wait Control Register (CS3WCR)
Initial value: H'0000 0500, Recommended set value: H'0000 2892
• Precharge completion wait cycles
WTRP[1:0] = B'01; 1 cycles
•
Wait cycles between ACTV command -> READ(A)/WRITE(A)command
WTRCD[1:0] =
B'10; 2 cycles
• Area 3 CAS latency
A3CL[1:0] = B'01; 2 cycles
• Precharge start wait cycles
TRWL[1:0] = B'10; 2 cycles
• Idle cycles between REF command/self-refresh deactivation
-> ACTV/REF/MRS command
WTRC[1:0] = B'10; 5 cycles
SDRAM Control Register (SDCR)
Initial value: H'0000 0000, Recommended set value: H'0000 0809
• Refresh control
RFSH = B'1; Refresh enabled
• Refresh control
RMODE = B'0; Auto refresh
• Bank active mode
BACTV = 0; Auto precharge mode
• Area 3 row address bits
A3ROW[1:0] = B'01; 12 bits
• Area 3 column address bits
A3COL[1:0] = B'01; 9 bits
Refresh Timer Control/Status Register (RTCSR)
Initial value: H'0000 0000, Recommended set value: H'A55A 0010
• Clock select
CKS[2:0] = B'010; B-φ/16
• Refresh times
RRC[2:0] = B'000; 1 time
Refresh Time Constant Register (RTCOR)
Initial value: H'0000 0000, Recommended set value: H'A55A 0041
* The following shows refresh request intervals in cases when clock
select is set to B- φ/16.
1 cycle: 240ns (66MHz/16 = 4.125MHz)
Refresh request intervals for the SDRAM: every 15.625µs
15.625µs/240ns = 64 (0x41) cycles per refresh
AC Characteristics Switching Register (ACSWR)
Initial value:
H'0000 0000,
Recommended set value:
H'0000 0009
• AC Characteristics Switch
ACOSW[3:0] = B'1001;
Switches characteristics and extends the
delay time