VI SDRAM CONTROLLER BLOCK: SDRAM INTERFACE
S1C33L03 FUNCTION PART
EPSON
B-VI-2-17
A-1
B-VI
SDRAM
Refresh Mode
The SDRAM controller supports two SDRAM refresh modes: auto refresh and self-refresh.
Auto refresh
The SDRAM controller incorporates a 12-bit auto refresh counter. This counter continues counting on OSC3
clock edges, and when a specified count is reached, commands are sent to the SDRAM that precharges and
auto-refreshes all banks. The counter is reset at that time, and starts counting for the next refresh period. The
counter is also reset by self-refresh.
The auto-refresh period is determined by the OSC3 clock frequency and the count value set in the SDRARFC
[11:0] (D[B:0])/Auto refresh count register (0x39FFC6). For SDRARFC, set the appropriate value meeting
the specifications of your SDRAM. The count value is obtained by the equation below.
RFP
SDRARFC
≤
––––––––
×
f
OSC3
- BL - CL - 2
×
t
RP
- t
RCD
- 3
ROWS
RFP:
Maximum refresh period [s]
ROWS: Row address size
f
OSC3
: OSC3 clock frequency [Hz]
BL:
Burst length [word]
CL:
CAS latency [Number of SD_CLK cycles]
t
RP
:
PRECHARGE command period [Number of SD_CLK cycles]
t
RCD
:
ACTIVE to READ or WRITE delay time [Number of SD_CLK cycles]
If RFP = 64 ms, ROWS = 4,096, f
OSC3
= 20 MHz, BL = 8, CL = 3, t
RP
= 4, and t
RCD
= 4, for example, the
value to set is calculated as follows:
0.064
SDRARFC
≤
––––––––
×
20,000,000 - 8 - 3 - 2
×
4 - 4 - 3 = 286
4,096
Therefore, set any value equal to or less than 286 (0x11E) for SDRARFC.
BCLK
Command
SDCKE
#SDCEx
#SDRAS
#SDCAS
#SDWE
SDBA[1:0]
SDA[10]
SDA[12:11, 9:0]
LDQM/HDQM
DQ[15:0]
REF
REF
NOP
H
L
NOP
NOP
PALL
NOP
t
RC
t
RP
Figure 2.15 Auto Refresh
Summary of Contents for CMOS 32-Bit Single Chip Microcomputer S1C33L03
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Page 15: ...S1C33L03 PRODUCT PART ...
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Page 147: ...S1C33L03 FUNCTION PART ...
Page 148: ......
Page 149: ...S1C33L03 FUNCTION PART I OUTLINE ...
Page 150: ......
Page 152: ...I OUTLINE INTRODUCTION B I 1 2 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 162: ...I OUTLINE LIST OF PINS B I 3 8 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 163: ...S1C33L03 FUNCTION PART II CORE BLOCK ...
Page 164: ......
Page 166: ...II CORE BLOCK INTRODUCTION B II 1 2 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 172: ...II CORE BLOCK CPU AND OPERATING MODE B II 2 6 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 176: ...II CORE BLOCK INITIAL RESET B II 3 4 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 224: ...II CORE BLOCK BCU Bus Control Unit B II 4 48 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 262: ...II CORE BLOCK DBG Debug Unit B II 7 2 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 263: ...S1C33L03 FUNCTION PART III PERIPHERAL BLOCK ...
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Page 266: ...III PERIPHERAL BLOCK INTRODUCTION B III 1 2 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 322: ...III PERIPHERAL BLOCK WATCHDOG TIMER B III 5 4 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 415: ...S1C33L03 FUNCTION PART IV ANALOG BLOCK ...
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Page 418: ...IV ANALOG BLOCK INTRODUCTION B IV 1 2 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 434: ...IV ANALOG BLOCK A D CONVERTER B IV 2 16 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 435: ...S1C33L03 FUNCTION PART V DMA BLOCK ...
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Page 438: ...V DMA BLOCK INTRODUCTION B V 1 2 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 492: ...V DMA BLOCK IDMA Intelligent DMA B V 3 18 EPSON S1C33L03 FUNCTION PART THIS PAGE IS BLANK ...
Page 493: ...S1C33L03 FUNCTION PART VI SDRAM CONTROLLER BLOCK ...
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Page 531: ...S1C33L03 FUNCTION PART VII LCD CONTROLLER BLOCK ...
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Page 579: ...S1C33L03 FUNCTION PART Appendix I O MAP ...
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