S16I — Store 16-bit

Instruction Word

Slot
Inst
6
3
6
2
6
1
6
0
5
9
5
8
5
7
5
6
5
5
5
4
5
3
5
2
5
1
5
0
4
9
4
8
4
7
4
6
4
5
4
4
4
3
4
2
4
1
4
0
3
9
3
8
3
7
3
6
3
5
3
4
3
3
3
2
3
1
3
0
2
9
2
8
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
1
9
1
8
1
7
1
6
1
5
1
4
1
3
1
2
1
1
1
0
9876543210
Format x24 - 24 bit(s) 0
S16I 0101 0010
t 3210
s 3210
imm8 76543210

Assembler Syntax

S16I at, as, 0..510

C Syntax

#include <xtensa/tie/xt_core.h>

extern void XT_S16I(short r, short * p, immediate i);

Description

(please consult the Xtensa ® Instruction Set Architecture Reference Manual for any cross references and additional information)

S16I is a 16-bit store from address register at to memory. It forms a virtual address by adding the contents of address register as and an 8-bit zero-extended constant value encoded in the instruction word shifted left by one. Therefore, the offset can specify multiples of two from zero to 510. Sixteen bits (two bytes) from the least significant half of the register are written to memory at the physical address.

If the Region Translation Option or the MMU Option is enabled, the virtual address is translated to the physical address. If not, the physical address is identical to the virtual address. If the translation or memory reference encounters an error (for example, protection violation or non-existent memory), the processor raises one of several exceptions .

Without the Unaligned Exception Option , the least significant bit of the address is ignored. A reference to an odd address produces the same result as a reference to the address, minus one. With the Unaligned Exception Option, such an access raises an exception.

Operation

vAddr ← AR[s] + (023||imm8||0)
Store16 (vAddr, AR[t]15..0)

Exceptions

Memory Store Group (see Memory Store Group:)

Implementation Pipeline

In Out
art Mstage, ars Estage

Protos that use S16I

proto S16I { in int16 r, in int16 * p, in immediate i }{}{
S16I r, p, i + 0;
}