STMicroelectronics SPEAr300, Reference Manual

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DDR memory controller (MPMC) RM0082
138/844 Doc ID 018672 Rev 1
mode. There will be at least a 15 cycle delay before the component being either fully
operational or enters the new low power mode.
Register programming
The low power modes of the Memory Controller are controlled by the lowpower_control and
lowpower_auto_enable parameters. These 5 bit parameters contain each one bit to control
each low power mode. The lowpower_control parameter enables the associated low power
mode, and the lowpower_auto_enable parameter sets the entry method into that mode as
manual or automatic.
Table 70 displays the relationship between the 5 bits of the
lowpower_control and lowpower_auto_enable parameters and the various low power
modes. Parameters meaning is discussed in
Section 10.14: Summary of memory controller
parameters .
When a lowpower_control parameter bit is set to 1'b1 by the user, the Memory Controller
checks the lowpower_auto_enable parameter.
●
If the associated bit in the lowpower_auto_enable parameter is set to 1'b1, the Memory
Controller will watch the associated counter for expiration and then enter that low power
mode.
● Table 71 shows the correlation between the low power modes and the counters that
control each mode's automatic entry.
●
If the associated bit in the lowpower_auto_enable parameter is cleared to 1'b0, the
Memory Controller will complete its current memory burst access and then enter the
specified low power mode.
Table 70. Low power mode parameters
Low Power Mode Enable Entry
Memory Power-Down (Mode 1) lowpower_control [4] =1'b1
lowpower_auto_enable [4]:
1'b0 = Manual
1'b1 = Automatic
Memory Power-Down with
Memory Clock Gating (Mode 2)
lowpower_control [3] =1'b1
lowpower_auto_enable [3]:
1'b0 = Manual
1'b1 = Automatic
Memory Self-Refresh (Mode 3) lowpower_control [2] =1'b1
lowpower_auto_enable [2]:
1'b0 = Manual
1'b1 = Automatic
Memory Self-Refresh with
Memory Clock Gating (Mode 4)
lowpower_control [1] =1'b1
lowpower_auto_enable [1]:
1'b0 = Manual
1'b1 = Automatic
Memory Self-Refresh with Memory and
Controller Clock Gating (Mode 5)
lowpower_control [0] =1'b1
lowpower_auto_enable [0]:
1'b0 = Manual
1'b1 = Automatic