GD32W51x User Manual
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cleared), the illegal access pulse is generated on a non-secure write access to the
DMA_CHxSCTL register which attempts to write 1 into any of the secure configuration
bits SECM, DSEC, SSEC.
When the software is switching from a secure state to a non-secure state (after the secure
transfer is completed), the secure software must disable the channel by a 32-bit write at the
DMA_CHxCTL address before switching. This operation is needed for the two below
reasons:
a non-secure software cannot do so.
the EN bit of the DMA_CHxCTL register must be cleared before the (non-secure)
software can reprogram the DMA_CHxCTL for a next transfer.
The dma_secm signal is asserted when any channels secure mode bit (SECMx) is set.
Privileged / unprivileged mode
The DMA controller performs AHB master transfers, with a privileged or unprivileged access
mode, at a channel level.
When a channel x is configured in privileged mode, the following access controls rules are
applied:
An unprivileged read access to a register field of this channel is forced to return 0, except
for both the privileged state and the secure state of this channel x (PRIV and SECM bits
of the DMA_CHxSCTL register) which are readable by an unprivileged software.
An unprivileged write access to a register field of this channel has no impact.
12.4.2.
Peripheral handshake
To ensure a well-organized and efficient data transfer, a handshake mechanism is introduced
between the DMA and peripherals, including a request signal and a acknowledge signal:
Request signal asserted by peripheral to DMA controller, indicating that the peripheral is
ready to transmit or receive data
Acknowledge signal responded by DMA to peripheral, indicating that the DMA controller
has initiated an AHB command to access the peripheral
Figure 12-3. Handshake mechanism
shows how the handshake mechanism works between
the DMA controller and peripherals.
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