Datasheet

101
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
12.6.4.5 LDR, PC-relative
Load register from memory.
Syntax
LDR{type}{cond} Rt, label
LDRD{cond} Rt, Rt2, label ; Load two words
where:
type is one of:
B unsigned byte, zero extend to 32 bits.
SB signed byte, sign extend to 32 bits.
H unsigned halfword, zero extend to 32 bits.
SH signed halfword, sign extend to 32 bits.
- omit, for word.
cond is an optional condition code, see “Conditional Execution” .
Rt is the register to load or store.
Rt2 is the second register to load or store.
label is a PC-relative expression. See “PC-relative Expressions” .
Operation
LDR loads a register with a value from a PC-relative memory address. The memory address is specified by a label
or by an offset from the PC.
The value to load or store can be a byte, halfword, or word. For load instructions, bytes and halfwords can either
be signed or unsigned. See “Address Alignment” .
label must be within a limited range of the current instruction. The table below shows the possible offsets between
label and the PC.
The user might have to use the .W suffix to get the maximum offset range. See “Instruction Width Selection” .
Restrictions
In these instructions:
 Rt can be SP or PC only for word loads
 Rt2 must not be SP and must not be PC
 Rt must be different from Rt2.
Table 12-19. Offset Ranges
Instruction Type Offset Range
Word, halfword, signed halfword, byte, signed byte -4095 to 4095
Two words -1020 to 1020