dsp56800e Freescale Semiconductor, Inc, dsp56800e Datasheet - Page 457

• Manufacturer Part Number: dsp56800e
• Description: 16-bit Digital Signal Controller Core
• Manufacturer: Freescale Semiconductor, Inc

DEC.BP
Operation:
D – 1 → D
Description: Decrement a byte value in memory. The value is internally sign extended to 20 bits before being dec-
Usage:
Example:
Explanation of Example:
Condition Codes Affected:
Freescale Semiconductor
Before Execution
Addresses
Byte
remented. The low-order 8 bits of the result are stored back to memory. The condition codes are cal-
culated based on the 8-bit result, with the exception of the E and U bits, which are calculated based on
the 20-bit result. Absolute addresses are expressed as byte addresses. The result is not affected by the
state of the saturation bit (SA).
This instruction is typically used when integer data is processed.
DEC.BP X:$3065
Prior to execution, the value at byte address X:$3065 is $00. Execution of the DEC.BP instruction dec-
rements this value by one and generates the result, $FF, with a borrow (the carry bit is set). The result
is negative since bit 7 is set. Note that this address is equivalent to the upper byte of word address
$1832.
E
U
N
Z
V
C
LF
15
— Set if the extension portion of the 20-bit result is in use
— Set if the 20-bit result is unnormalized
— Set if bit 7 of the result is set
— Set if the result is zero
— Set if overflow has occurred in result
— Set if a carry (or borrow) occurs from bit 7 of the result
(no parallel move)
$3068
$3066
$3064
$3062
P4
14
SR
13
P3
7
Decrement Byte (Byte Pointer)
88
66
00
22
X Memory
P2
12
MR
0300
0
P1
11
7
77
55
33
11
P0
10
Instruction Set Details
0
; decrement the byte at (byte) address $3065
I1
9
Assembler Syntax:
DEC.BP
I0
8
SZ
7
After Execution
Addresses
6
L
Byte
5
E
D
U
4
CCR
$3068
$3066
$3064
$3062
SR
N
3
(no parallel move)
7
2
Z
FF
88
66
22
X Memory
0319
V
1
0
7
DEC.BP
C
0
77
55
33
11
0
A-113