GD32F20x User Manual
705
3-2
NRTP
0x1
1
NRMUX
0x1, Depends on users
0
NRBKEN
0x1
EXMC_SNTCFGx(Write)
31-30
Reserved
0x0
29-28
ASYNCMOD
0x0
27-24
DLAT
Data latency
23-20
CKDIV
The figure above: 0x1,EXMC_CLK=2HCLK
19-16
BUSLAT
Time between EXMC_NE[x] rising edge to
EXMC_NE[x] falling edge
15-8
DSET
No effect
7-4
AHLD
No effect
3-0
ASET
No effect
SPI/QPI-PSRAM access timing diagram
SPI/QPI-PSRAM is controlled by EXMC memory bank0, region 0 only, it is a PSRAM with
SPI and QPI interface, consisting of 6 IOs, the chip-enable, clock, and 4 data IOs, and they
are summarized in the following table.
Table 25-16. SPI/QPI interface
Signal
Direction
SPI Mode
QPI Mode
EXMC_CLK
O
Serial Clock
EXMC_NE[0]
O
Chip-Enable (active low)
EXMC_D[0]
IO
Serial Output
Data IO[0]
EXMC_D[1]
IO
Serial Input
Data IO[1]
EXMC_D[2]
IO
X
Data IO[2]
EXMC_D[3]
IO
X
Data IO[3]
1.
Controller initialization
In the beginning, users should program the SPI initialization register EXMC_SINIT. Data
sampling clock edge is selected via the POL bit, read device ID length could be configured
by the IDL bit, address bit number is controlled by the ADRBIT, and command bit number is
set by CMDBIT.
2.
Read/Write operation
Three modes of memory access are possible, SPI, QPI, and SQPI. Access mode should be
configured before read/write operations. Read/write command mode is programmed by the
RMODE and WMODE, wait cycle is controlled by the RWAITCYCLE and WWAITCYCLE bit,
and the specific memory operating command should be programmed in RCMD and WCMD
bit, these read/write settings are located in EXMC_SRCMD and EXMC_SWCMD registers
respectively.
After memory access mode configuration, read/write is the same as accessing ordinary NOR
Flash, data to be transferred to the external memory is written into EXMC bank0, region0,
Содержание GD32F20 Series
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