3-44
Computer Group Literature Center Web Site
System Memory Controller (SMC)
3
CLK Frequency Register
CLK FREQUENCY
These bits should be programmed with the hexadecimal
value of the operating CLOCK frequency in MHz (i.e. $42
for 66 MHz). When these bits are programmed this way,
the chip’s prescale counter produces a 1 MHz
(approximate) output. The output of the chip prescale
counter is used by the refresher/scrubber and the 32-bit
counter. After power-up, this register is initialized to $64
(for 100 MHz). The formula is:
Counter_Output_Frequency = (Clock
Frequency)/CLK_FREQUENCY
For example, if the Clock Frequency is 100 MHz and
CLK_FREQUENCY is $64, then the counter output
frequency is 100 MHz/100 = 1 MHz.
When the CLK pin is operating slower than 100MHz,
software should program CLK_FREQUENCY to be at
least as slow as the CLK pin’s frequency as soon as
possible after power-up reset so that SDRAM refresh does
not get behind. It is okay for the software then to take
some time to “up” CLK_FREQUENCY to the correct
value. Refresh will get behind only when the actual CLK
pin’s frequency is lower than the value programmed into
CLK_FREQUENCY.
por
por is set by the occurrence of power up reset. It is cleared
by writing a one to it. Writing a 0 to it has no effect.
Address
$FEF80020
Bit
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Name
CLK FREQUENCY
0
0
0
0
0
0
0
po
r
Operation
READ/WRITE
READ ZERO
READ ZERO
R
R
R
R
R
R
R
R/
C
Reset
64 P
X
X
X
X
X
X
X
X
X
1 P
Summary of Contents for MVME5100 Series
Page 1: ...MVME5100 Single Board Computer Programmer s Reference Guide V5100A PG2 September 2001 Edition ...
Page 16: ...xvi ...
Page 20: ...xx ...
Page 28: ...xxviii ...
Page 62: ...1 34 Computer Group Literature Center Web Site Product Data and Memory Maps 1 ...
Page 278: ...3 88 Computer Group Literature Center Web Site System Memory Controller SMC 3 ...
Page 288: ...4 10 Computer Group Literature Center Web Site Hawk Programming Details 4 ...
Page 320: ...Index IN 12 Computer Group Literature Center Web Site I N D E X ...