XC2200 Derivatives
System Units (Vol. 1 of 2)
Central Processing Unit (CPU)
User’s Manual
4-56
V2.1, 2008-08
CPUSV2_X, V2.2
4.8
Standard Data Processing
All standard arithmetic, shift-, and logical operations are performed in the 16-bit ALU. In
addition to the standard functions, the ALU of the XC2200 includes a bit-manipulation
unit and a multiply and divide unit. Most internal execution blocks have been optimized
to perform operations on either 8-bit or 16-bit numbers. After the pipeline has been filled,
most instructions are completed in one CPU cycle. The status flags are automatically
updated in register PSW after each ALU operation and reflect the current state of the
microcontroller. These flags allow branching upon specific conditions. Support of both
signed and unsigned arithmetic is provided by the user selectable branch test. The
status flags are also preserved automatically by the CPU upon entry into an interrupt or
trap routine. Another group of bits represents the current CPU interrupt status. Two
separate bits (USR0 and USR1) are provided as general purpose flags.
PSW
Processor Status Word
SFR
Reset Value: 0000
H
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
ILVL
IEN
HLD
EN
BANK
USR
1
USR
0
MUL
IP
E
Z
V
C
N
rwh
rw
rw
rwh
rwh rwh
r
rwh rwh rwh rwh rwh
Field
Bits
Type
Description
ILVL
[15:12] rwh
CPU Priority Level
0H
Lowest Priority
…
…
FH
Highest Priority
IEN
11
rw
Global Interrupt/PEC Enable Bit
0
Interrupt/PEC requests are disabled
1
Interrupt/PEC requests are enabled
HLDEN
10
rw
Hold Enable
0
External bus arbitration disabled
1
External bus arbitration enabled
Note: The selected arbitration mode is activated
when HLDEN is set for the first time.
BANK
[9:8]
rwh
Reserved for Register File Bank Selection
00
Global register bank
01
Reserved
10
Local register bank 1
11
Local register bank 2