MPC8540 datasheet(397/1302 Pages) FREESCALE

397 / 1302 page

Functional Description

MPC8540 PowerQUICC III Integrated Host Processor Reference Manual, Rev. 1

Freescale Semiconductor

9-43

System software is responsible for optimal configuration of TIMING_CFG_1 [REFREC] at reset.

Configuration must be completed before DDR SDRAM accesses are attempted.

9.5.8.2

DDR SDRAM Refresh and Power-Saving Modes

In full-on mode, the DDR memory controller supplies the normal auto refresh to SDRAM. In sleep

mode, the DDR memory controller can be configured to take advantage of self-refreshing

SDRAMs or to provide no refresh support. Self-refresh support is enabled with the SREN memory

control parameter of the DDR_SDRAM_CFG register. Table 9-30 summarizes the refresh types

available in each power-saving mode.

Note that in the absence of refresh support, system software must preserve DDR SDRAM data

(such as by copying the data to disk) before entering the power-saving mode.

All open pages are precharged before self refresh mode is entered.

The dynamic power-saving mode uses the CKE DDR SDRAM pin to dynamically power down

when there is no system memory activity. The CKE pin is negated when both of the following

conditions are met:

•

No memory refreshes are scheduled.

•

No memory accesses are scheduled.

CKE is reasserted when a new access or refresh is scheduled or the dynamic power mode is

disabled. This mode is controlled with DDR_SDRAM_CFG[DYN_PWR].

Dynamic power management mode offers tight control of the memory system’s power

consumption by trading power for performance through the use of

DDR_SDRAM_INTERVAL[BSTOPRE]. Powering up the DDR SDRAM when a new memory

reference is scheduled causes a one-clock access latency penalty, as shown in Figure 9-34.

Figure 9-34. DDR SDRAM Power-Down Mode

Table 9-30. DDR SDRAM Power-Saving Modes Refresh Configuration

Power Saving

Mode

Refresh

Type

SREN

Sleep

Self

None

Mem Bus Clock

NOP

COMMAND

ACT

CKE

MPC8540 Datasheet(PDF) 397 Page - Freescale Semiconductor, Inc

MPC8540 Datasheet(HTML) 397 Page - Freescale Semiconductor, Inc

Html Pages

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 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL