Subtract and round (dalu), Operation assembler syntax – Freescale Semiconductor StarCore SC140 User Manual
Page 698
A-384
SC140 DSP Core Reference Manual
SBR
SBR
Subtract And Round (DALU)
SBR
Description
Status and Conditions that Affect Instruction
Status and Conditions Changed by Instruction
Example
sbr d3,d0
Operation
Assembler Syntax
Rnd(Dn – Da)
→ Dn
SBR Da,Dn
SBR Da,Dn
Subtracts the first data register (Da) of a pair from the second (Dn), then rounds the result and stores the
result in the second data register (Dn). Rounding adjusts the LSB of the high part of the destination register
according to the value of the low part of the register, and then zeros the low part. The two modes of the
round function, Rnd(), are described on page A-359.
Register Address
Bit Name
Description
SR[2]
SM
If set, selects 32-bit arithmetic saturation mode.
SR[3]
RM
Rounding mode
SR[5:4]
S[1:0]
Scaling bits determine which bits in the result are used in the Ln bit
calculation and which bits are used in rounding.
Register Address
Bit Name
Description
EMR[2]
DOVF
Set if the result cannot be represented in 40 bits, or if the result
saturates to 32 bits in arithmetic saturation mode.
Ln
L
If not in arithmetic saturation mode (SR [SM] = 0), calculates and
updates the Ln bit in the destination register. If in arithmetic
saturation mode (SR [SM] = 1), clears the Ln bit in the destination
register.
Register/Memory Address
Before
After
SR
$00E0 0000
D3
$00 1539 0030
L0:D0
$0:$00 2AE7 0080
$0:$00 15AE 0000
EMR
$0000 0000