GD32W51x User Manual
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Figure 22-3. CSN and SCK behavior
SCK
CSN
T
T
When the FIFO stays empty in a write command, or full in a read command, SCK will be
stalled and stays low until the FIFO can work again. At this moment if the CSN is high, SCK
will rises back up one half of a SCK cycle after the rising edge of the CSN.
22.4.
Operating modes
22.4.1.
Indirect mode
In indirect write mode, data to be transmitted are written into DATA. While in indirect read
mode, data to be received are read from DATA.
DTLEN field (QSPI_DTLEN register) defines the number of byte to be transferred. If DTLEN
= 0xFFFF_FFFF, the number of data is considered undefined, the transmission continues
until the memory size boundary is reach as specified by FMSZ. If both DTLEN =
0xFFFF_FFFF and FMSZ = 0x1F, then the transmission continues indefinitely until the QSPI
is disabled.
Transfer complete flag TC is set when the number of byte programed in DTLEN is reached,
in case of undefined transfer length, TC is set when the transmit/received byte number equals
to external memory size. An interrupt is generated if TCIE and TC are both set, and it is
cleared by setting TCC to 1.
Trigger a command sequence
The command sequence starts immediately after the last information is provided by software
according to communication requirement.
When neither address nor data are required, the sequence start immediately after TCFG has
be accessed.
When address is required and no data is required, the sequence starts after ADDR has been
accessed.
When both address and data are required in indirect write mode, the command sequence
starts after DATA has been accessed.