Or t – Digi NS9750 User Manual
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R e g i s t e r s
2 2 0
N S 9 7 5 0 H a r d w a r e R e f e r e n c e
Dynamic Memory Auto Refresh Period register
Address: A070 004C
The Dynamic Memory Auto Refresh Period register allows you to program the auto-
refresh period and the auto-refresh to active command period, t
RFC
. It is
recommended that this register be modified during initialization, or when there are
no current or outstanding transactions. Wait until the memory controller is idle, then
enter low-power or disabled mode. This value normally is found in SDRAM datasheets
as t
RFC
or t
RC
.
Note:
The Dynamic Memory Auto Refresh Period register is used for all four
dynamic memory chip selects. The worst case value for all chip selects
must be programmed.
Register bit assignment
Bits
Access
Mnemonic
Description
D31:05
N/A
Reserved
N/A (do not modify)
D04:00
R/W
RFC
Auto-refresh period and auto-refresh to active command period
0x0–0x1E
n+1 clock cycles, where the delay is in
CLK
cycles.
0x1F
32 clock cycles (reset value on
reset_n
)
Table 151: Dynamic Memory Auto Refresh Period register
13
12
11
10
9
8
7
6
5
4
3
2
1
0
15
14
31
29
28
27
26
25
24
23
22
21
20
19
18
17
16
30
Reserved
Reserved
RFC