SMC Networks PL241 Memory manager operation, Low-power operation Chip configuration registers

Models: AHB SRAM/NOR PL241

1 110
Download 110 pages 44.4 Kb
Page 42
Image 42
2.4.6Memory manager operation

Functional Overview

2.4.6Memory manager operation

The memory manager module is responsible for controlling the state of the SMC and the updating of chip configuration registers.

This subsection describes:

Low-power operation

Chip configuration registers

Direct commands on page 2-24.

Low-power operation

The SMC accepts requests to enter the Low-power state through either the SMC low-power interface or the APB register interface.

The SMC does not enter the power-down state until it has received an idle indication from all areas of the peripheral, that is:

there is no valid transfer held in the Format block

there are no valid transfers held in the SMC interface

all FIFOs are empty

all memory interface blocks are IDLE.

When the Low-power state is entered, no new memory transfers are accepted until the SMC has been moved out of Low-power state. The SMC does not request to move out of Low-power state, and never refuses a power-down request.

Chip configuration registers

The SMC provides a mechanism for synchronizing the switching of operating modes of the SMC with that of the memory device.

The smc_set_cycles Register and smc_set_opmode Register act as holding registers for new operating parameters until the SMC detects the memory device has switched modes.

Figure 2-11 on page 2-23shows the memory manager containing a bank of registers for each memory chip supported by the SMC. The manager register bank consists of all the timing parameters smc_sram_cycles0_<0-3> and smc_opmode0_<0-3>, that are required for the controller to correctly time any type of access to a supported memory type.

2-22

Copyright © 2006 ARM Limited. All rights reserved.

ARM DDI 0389B

Page 42
Image 42
SMC Networks PL241 Memory manager operation, Low-power operation Chip configuration registers, Direct commands on page