收藏本站
RM0008
Caution:
Flexible static memory controller (FSMC)
Data latency versus NOR Flash latency
The data latency is the number of cycles to wait before sampling the data. The DATLAT
value must be consistent with the latency value specified in the NOR Flash configuration
register. The FSMC does not include the clock cycle when NADV is low in the data latency
count.
Some NOR Flash memories include the NADV Low cycle in the data latency count, so the
exact relation between the NOR Flash latency and the FMSC DATLAT parameter can be
either of:
●
●
NOR Flash latency = DATLAT + 2
NOR Flash latency = DATLAT + 3
Some recent memories assert NWAIT during the latency phase. In such cases DATLAT can
be set to its minimum value. As a result, the FSMC samples the data and waits long enough
to evaluate if the data are valid. Thus the FSMC detects when the memory exits latency and
real data are taken.
Other memories do not assert NWAIT during latency. In this case the latency must be set
correctly for both the FSMC and the memory, otherwise invalid data are mistaken for good
data, or valid data are lost in the initial phase of the memory access.
Single-burst transfer
When the selected bank is configured in synchronous burst mode, if an AHB single-burst
transaction is requested, the FSMC performs a burst transaction of length 1 (if the AHB
transfer is 16-bit), or length 2 (if the AHB transfer is 32-bit) and de-assert the chip select
signal when the last data is strobed.
Clearly, such a transfer is not the most efficient in terms of cycles (compared to an
asynchronous read). Nevertheless, a random asynchronous access would first require to re-
program the memory access mode, which would altogether last longer.
Wait management
For synchronous burst NOR Flash, NWAIT is evaluated after the programmed latency
period, (DATALAT+1) CLK clock cycles.
If NWAIT is sensed active (low level when WAITPOL = 0, high level when WAITPOL = 1),
wait states are inserted until NWAIT is sensed inactive (high level when WAITPOL = 0, low
level when WAITPOL = 1).
When NWAIT is inactive, the data is considered valid either immediately (bit WAITCFG = 1)
or on the next clock edge (bit WAITCFG = 0).
During wait-state insertion via the NWAIT signal, the controller continues to send clock
pulses to the memory, keeping the chip select and output enable signals valid, and does not
consider the data valid.
There are two timing configurations for the NOR Flash NWAIT signal in burst mode:
●
●
Flash memory asserts the NWAIT signal one data cycle before the wait state (default
after reset)
Flash memory asserts the NWAIT signal during the wait state
These two NOR Flash wait state configurations are supported by the FSMC, individually for
each chip select, thanks to the WAITCFG bit in the FSMC_BCRx registers (x = 0..3).
Doc ID 13902 Rev 9
431/995
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
MCBTMPM330 BOARD EVAL TOSHIBA TMPM330 SER
MCIMX25WPDKJ KIT DEVELOPMENT WINCE IMX25
MCIMX53-START-R KIT DEVELOPMENT I.MX53
MCM69C432TQ20 IC CAM 1MB 50MHZ 100LQFP
MCP1401T-E/OT IC MOSFET DRVR INV 500MA SOT23-5
MCP1403T-E/MF IC MOSFET DRIVER 4.5A DUAL 8DFN
MCP1406-E/SN IC MOSFET DVR 6A 8SOIC
MCP14628T-E/MF IC MOSFET DVR 2A SYNC BUCK 8-DFN
相关代理商/技术参数
MCBSTM32EXLU 功能描述:开发板和工具包 - ARM EVAL BOARD + ULINK2 FOR STM32F103ZG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32EXLU-ED 制造商:ARM Ltd 功能描述:KEIL STM STM32EXL EVAL BOARD
MCBSTM32EXLUME 功能描述:开发板和工具包 - ARM EVAL BOARD + ULINKME FOR STM32F103ZG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F207IG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200U 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F207IG + ULINK2 RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200UME 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F207IG ULINK-ME RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200UME-ED 制造商:ARM Ltd 功能描述:KEIL STM32F207IG EVAL BOARD
MCBSTM32F400 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F407IG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V