GD32F10x User Manual
603
1. Data latency and NOR Flash latency
Data latency is the number of EXMC_CLK cycles to wait before sampling the data. The
relationship between data latency and NOR Flash specification’s latency parameter is as
follows:
For NOR Flash’s specification excluding the EXMC_NADV cycle, their relationship should be:
NOR Flash latency=DLAT+2 (20-6)
For NOR Flash’s specification including the EXMC_NADV cycle, their relationship should be:
NOR Flash latency=DLAT+3 (25-7)
2. Data wait
Users should guarantee that EXMC_NWAIT signal matches that of the external device. This
signal is configured through the EXMC_SNCTLx registers, it is enabled by the NRWTEN bit,
and the active timing could be one data cycle before the wait state or active during the active
stat
e by the configuration NRWTCFG bit, while the wait signal’s polarity is set by the
NRWTPOL bit.
In NOR Flash synchronous burst access mode, when NRWTEN bit in EXMC_SNCTLx
register is set, EXMC_NWAIT signal will be detected after a period of data latency. If
EXMC_NWAIT signal detected is valid, wait cycles will be inserted until EXMC_NWAIT
becomes invalid.
The valid polarity of EXMC_NWAIT:
NRWTPOL= 1: valid level of EXMC_NWAIT signal is high.
NRWTPOL= 0: valid level of EXMC_NWAIT signal is low.
In synchronous burst mode, EXMC_NWAIT signal has two kinds of configurations:
NRWTCFG = 1: When EXMC_NWAIT signal is active, current cycle data is not valid.
NRWTCFG = 0: When EXMC_NWAIT signal is active, the next cycle data is not valid. It is
the default state after reset.
During wait-state inserted via the EXMC_NWAIT signal, the controller continues to send clock
pulses to the memory, keep the chip select and output signals availably, and ignore the invalid
data signal.
3. Mode SM - Single burst transmission
For synchronous burst transmission, if the needed data of AHB is 16-bit, EXMC will perform
a burst transmission whose length is 1. If the needed data of AHB is 32-bit, EXMC will make
the transmission divided into two 16-bit transmissions, that is, EXMC performs a burst
transmission whose length is 2.
For other configurations please refers to
Summary of Contents for GD32F10 Series
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Page 416: ...GD32F10x User Manual 416 shadow register updates every update event ...
Page 427: ...GD32F10x User Manual 427 value ...
Page 518: ...GD32F10x User Manual 518 These bits are not used in SPI mode ...