Data Sheet

365
Atmel | SMART SAM D21 [DATASHEET]
Atmel-42181G–SAM-D21_Datasheet–09/2015
21.8.1 Control A
Name: CTRLA
Offset: 0x00
Reset: 0x0000
Property: Write-Protected
z Bits 15:8 – CMDEX[7:0]: Command Execution
This bit group should be written with the key value 0xA5 to enable the command written to CMD to be executed. If
the bit group is written with a different key value, the write is not performed and the PROGE status bit is set.
PROGE is also set if the a previously written command is not complete.
The key value must be written at the same time as CMD. If a command is issued through the APB bus on the
same cycle as an AHB bus access, the AHB bus access will be given priority. The command will then be executed
when the NVM block and the AHB bus are idle.
The READY status must be one when the command is issued.
Bit 0 of the CMDEX bit group will read back as one until the command is issued.
Table 21-5. Command Execution
z Bit 7 – Reserved
This bit is unused and reserved for future use. For compatibility with future devices, always write this bit to zero
when this register is written. This bit will always return zero when read.
z Bits 6:0 – CMD[6:0]: Command
These bits define the command to be executed when the CMDEX key is written, as shown in Table 21-6.
Bit 151413121110 9 8
CMDEX[7:0]
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000
Bit 76543210
CMD[6:0]
Access R R/W R/W R/W R/W R/W R/W R/W
Reset00000000
CMDEX[7:0] Name Description
0x0-0xA4 Reserved
0xA5 KEY Execution Key
0xA6-0xFF Reserved