Motorola MVME5100 用户手册
Programming Model
http://www.motorola.com/computer/literature
3-45
3
us (64 ms / 8192 rows = 7.8 us). In order for Hawk 1 or 2
to accommodate such SDRAM’s their
CLK_FREQUENCY must be programmed with the CLK
pin (bus clock) frequency divided by two. For example, if
the clock pin frequency is 100 MHz, the
CLK_FREQUENCY register should be programmed
with $32 (100 MHz divided by 2) rather than $64. The
same work-around can, but does not have to be used for
Hawk 3. Hawk 3 includes an additional control bit (drr)
that when set, removes the need for the work-around.
Refer to the following explanation of the drr bit.
to accommodate such SDRAM’s their
CLK_FREQUENCY must be programmed with the CLK
pin (bus clock) frequency divided by two. For example, if
the clock pin frequency is 100 MHz, the
CLK_FREQUENCY register should be programmed
with $32 (100 MHz divided by 2) rather than $64. The
same work-around can, but does not have to be used for
Hawk 3. Hawk 3 includes an additional control bit (drr)
that when set, removes the need for the work-around.
Refer to the following explanation of the drr bit.
drr
Double Refresh Rate (Hawk 3 only) When drr is set,
Hawk3’s refresh rate doubles. When drr is cleared,
Hawk3’s refresh rate is normal and matches that of Hawk
1 and 2. Refer to the following examples of DRR and
CLK_FREQUENCY settings with the resulting refresh
rates:
Hawk3’s refresh rate doubles. When drr is cleared,
Hawk3’s refresh rate is normal and matches that of Hawk
1 and 2. Refer to the following examples of DRR and
CLK_FREQUENCY settings with the resulting refresh
rates:
7.8us corresponds to 64ms per 8192 rows and 15.6us
corresponds to 64ms per 4096 rows.
corresponds to 64ms per 4096 rows.
Note
MVME5100 boards are 100 MHz SBCs.
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.
by writing a one to it. Writing a 0 to it has no effect.
drr
value
CLK pin
frequency
CLK_FREQUENCY
value
Refresh
Period
Comments
0
100 MHz
$32
7.8us
Hawk1, 2 or 3
0
100 MHz
$64
15.6us
Hawk1, 2 or 3
1
100 MHz
$64
7.8us
Hawk3 only
0
66 MHz
$21
7.8us
Hawk1, 2 or 3
0
66 MHz
$42
15.6us
Hawk1, 2 or 3
1
66 MHz
$42
7.8us
Hawk3 only