Communication between these clock domains must be synchronized. This mechanism is implemented in
hardware, so the synchronization process takes place even if the peripheral generic clock is running from
the same clock source and on the same frequency as the bus interface.
All registers in the bus interface are accessible without synchronization.
All registers in the peripheral core are synchronized when written. Some registers in the peripheral core
are synchronized when read.
Each individual register description will have the properties "Read-Synchronized" and/or "Write-
Synchronized" if a register is synchronized.
As shown in the figure below, each register that requires synchronization has its individual synchronizer
and its individual synchronization status bit in the Synchronization Busy register (SYNCBUSY).
Note:
For registers requiring both read- and write-synchronization, the corresponding bit in SYNCBUSY
is shared.
Figure 15-3. Register Synchronization Overview
Synchronous Domain
(CLK_APB)
Asynchronous Domain
(GCLK )
Non Sync’d reg
Periperal Bus
Write-Sync’d reg
SYNCBUSY
R/W-Sync’d reg
Sync
Sync
Read-Sync’d reg
Sync
Write-only register
Read-only register
R/W register
Write-Sync’d reg
Sync
R/W register
Non Sync’d reg
Read-only register
Sync
INTFLAG
15.3.2. General Write Synchronization
Write-Synchronization is triggered by writing to a register in the peripheral clock domain. The respective
bit in the Synchronization Busy register (SYNCBUSY) will be set when the write-synchronization starts
and cleared when the write-synchronization is complete. Refer to
for details on the
synchronization delay.
When write-synchronization is ongoing for a register, any subsequent write attempts to this register will be
discarded, and an error will be reported.
Atmel SAM L22G / L22J / L22N [DATASHEET]
Atmel-42402E-SAM L22G / L22J / L22N_Datasheet_Complete-07/2016
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