日志

cortexM3r的memory系统

已有 1228 次阅读| 2016-6-24 17:55 |个人分类:LINUX

地址映射图

Memory map	Region
code	Instruction fetches are performed over the ICode bus. Data accesses are performed over the DCode bus
SRAM	Instruction fetches and data accesses are performed over the System bus.
SRAM bit-band	Alias region .data accesses are aliases. Instruction accesses are not aliases
Peripheral	Instruction fetches and data accesses are performed over the system bus
Peripheral bit-band	Alias region. data accesses are aliases. Instruction accesses are not aliases
External RAM	Instruction fetches and data accesses are performed over the System bus.
External device	Instruction fetches and data accesses are performed over the System bus.
Private peripheral bus	External and internal private peripheral (PPB) interface. See private peripheral bus. This memory region is execute never(XN) and so instruction fetches are prohibited. An MPU, if present cannot change this .
System	System segment for vendor system peripherals. This memory region is XN, and so instruction fetches are prohibited. An MPU ,

地址空间可以通过另一种方式分为 8 个 512MB 等份：
1. 代码区（ 0x0000_0000- 0x1FFF_FFFF）。该区是可以执行指令的，缓存属性为 WT（ “写通”，Write Through），即不可以缓存。此区亦允许布设数据存储器。在此区上的数据操作是通过数据总线接口的（估计读数据使用 D-Code，写数据使用 System），且在此区上的写操作是缓冲的。
2. SRAM 区（ 0x2000_0000 – 0x3FFF_FFFF）。此区用于片内 SRAM，写操作是缓冲的，并且可以选择 WB-WA(Write Back, Write Allocated)缓存属性。此区亦可以执行指令，以允许把代码拷贝到内存中执行——常用于固件升级等维护工作。
3. 片上外设区(0x4000_0000 – 0x5FFF_FFFF)。该区用于片上外设，因此是不可缓存的，也不可以在此区执行指令（这也称为 eXecute Never, XN。 arm 的参考手册大量使用此术语）。
4. 外部 RAM 区的前半段（ 0x6000_0000 - 0x7FFF_FFFF）。该区可用于布设片上 RAM 或片外 RAM，可缓存（缓存属性为 WB-WA），并且可以执行指令.