Datasheet

173
SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
• VECTCLRACTIVE
WO
Reserved for Debug use. This bit reads as 0. When writing to the register you must write 0 to this bit, otherwise behavior is
Unpredictable.
• VECTRESET
WO
Reserved for Debug use. This bit reads as 0. When writing to the register you must write 0 to this bit, otherwise behavior is
Unpredictable.
10.21.6.1 Binary point
The PRIGROUP field indicates the position of the binary point that splits the PRI_n fields in the Interrupt Priority
Registers into separate group priority and subpriority fields. Table 10-31 shows how the PRIGROUP value controls
this split.
Determining preemption of an exception uses only the group priority field, see “Interrupt priority grouping” on page
75.
Table 10-31. Priority grouping
Interrupt priority level value, PRI_N[7:0] Number of
PRIGROUP Binary point
(1)
1. PRI_n[7:0] field showing the binary point. x denotes a group priority field bit, and y denotes a subpriority field bit.
Group priority bits Subpriority bits Group priorities Subpriorities
b011 bxxxx.0000 [7:4] None 16 1
b100 bxxx.y0000 [7:5] [4] 8 2
b101 bxx.yy0000 [7:6] [5:4] 4 4
b110 bx.yyy0000 [7] [6:4] 2 8
b111 b.yyyy0000 None [7:4] 1 16