你好:
最近在使用CC2640R2F 时候 在SPI总线上挂载两个SPI设备,当把SPI速率设置为12MHZ 时候,一切正常,但是如果把SPI速率设置为24MHZ 时候,常温下没有问题,但是温度上升到50 多摄氏度时候,SPI通讯就有问题。
在TI的提供的datasheet 中看到上面提到SSI 最大时钟为 系统时钟的8分频(在MASTER TX&RX 模式下)即 6MHz
但是在另外一份文档 “CC13x0, CC26x0 SimpleLink™ Wireless MCUTechnical Reference Manual “” 中第1486 页提到 “For master mode, the core clock (PERDMACLK) must be at least two times faster than SSIn_CLK. 这样看来系统时钟只需要2倍SSI CLK 时钟就可以了 也就是说SPI时钟可以到 48/2 =24MHz 。
那么请问 :
1:CC2640R2F SPI Master 模式最大时钟可以到多少
2:两份文档为何有差异
谢谢
Viki Shi:
TRM 文档里写了:The SSI includes a programmable bit rate clock divider and prescaler to generate the serial output clock. The bit rates are supported to 2 MHz and higher, with maximum bit rate is determined by peripheral devices.
在SPICC26XXDMA.h定义如下:
## Data Frames #
*
* SPI data frames can be any size from 4-bits to 16-bits. If the dataSize in
* ::SPI_Params is greater that 8-bits, then the *** driver
* implementation will assume that the ::SPI_Transaction txBuf and rxBuf
* point to an array of 16-bit uint16_t elements.
*
* dataSize | buffer element size |
* ——– | ——————- |
* 4-8 bits | uint8_t |
* 9-16 bits | uint16_t |
*
**********************************************************************************************************
* ## Bit Rate ##
* When the SPI is configured as SPI slave, the maximum bit rate is 4MHz.
*
* When the SPI is configured as SPI master, the maximum bit rate is 12MHz.
**************************************************************************************************************