diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/SPI/README.dual-flash | 65 |
1 files changed, 65 insertions, 0 deletions
diff --git a/doc/SPI/README.dual-flash b/doc/SPI/README.dual-flash new file mode 100644 index 0000000..ba0aa26 --- /dev/null +++ b/doc/SPI/README.dual-flash @@ -0,0 +1,65 @@ +SPI/QSPI Dual flash connection modes: +===================================== + +This describes how SPI/QSPI flash memories are connected to a given +controller in a single chip select line. + +Current spi_flash framework supports, single flash memory connected +to a given controller with single chip select line, but there are some +hw logics(ex: xilinx zynq qspi) that describes two/dual memories are +connected with a single chip select line from a controller. + +"dual_flash" from include/spi.h describes these types of connection mode + +Possible connections: +-------------------- +SF_SINGLE_FLASH: + - single spi flash memory connected with single chip select line. + + +------------+ CS +---------------+ + | |----------------------->| | + | Controller | I0[3:0] | Flash memory | + | SPI/QSPI |<======================>| (SPI/QSPI) | + | | CLK | | + | |----------------------->| | + +------------+ +---------------+ + +SF_DUAL_STACKED_FLASH: + - dual spi/qspi flash memories are connected with a single chipselect + line and these two memories are operating stacked fasion with shared buses. + - xilinx zynq qspi controller has implemented this feature [1] + + +------------+ CS +---------------+ + | |---------------------->| | + | | I0[3:0] | Upper Flash | + | | +=========>| memory | + | | | CLK | (SPI/QSPI) | + | | | +---->| | + | Controller | CS | | +---------------+ + | SPI/QSPI |------------|----|---->| | + | | I0[3:0] | | | Lower Flash | + | |<===========+====|====>| memory | + | | CLK | | (SPI/QSPI) | + | |-----------------+---->| | + +------------+ +---------------+ + + - two memory flash devices should has same hw part attributes (like size, + vendor..etc) + - Configurations: + on LQSPI_CFG register, Enable TWO_MEM[BIT:30] on LQSPI_CFG + Enable U_PAGE[BIT:28] if U_PAGE flag set - upper memory + Disable U_PAGE[BIT:28] if U_PAGE flag unset - lower memory + - Operation: + accessing memories serially like one after another. + by default, if U_PAGE is unset lower memory should accessible, + once user wants to access upper memory need to set U_PAGE. + +Note: Technically there is only one CS line from the controller, but +zynq qspi controller has an internal hw logic to enable additional CS +when controller is configured for dual memories. + +[1] http://www.xilinx.com/support/documentation/user_guides/ug585-Zynq-7000-TRM.pdf + +-- +Jagannadha Sutradharudu Teki <jaganna@xilinx.com> +05-01-2014. |