mcf51ac256a Freescale Semiconductor, Inc, mcf51ac256a Datasheet - Page 136

• Manufacturer Part Number: mcf51ac256a
• Description: Mcf51ac Flexis
• Manufacturer: Freescale Semiconductor, Inc

ColdFire Core
7.2.5
The PC contains the currently executing instruction address. During instruction execution and exception
processing, the processor automatically increments PC contents or places a new value in the PC. The PC
is a base address for PC-relative operand addressing.
The PC is initially loaded during reset exception processing with the contents at location 0x(00)00_0004.
7.2.6
The VBR contains the base address of the exception vector table in the memory. To access the vector table,
the displacement of an exception vector is added to the value in VBR. The lower 20 bits of the VBR are
not implemented by ColdFire processors. They are assumed to be zero, forcing the table to be aligned on
a 1 MB boundary.
7-6
In addition, because the V1 ColdFire core supports a 16 MB address space, the upper byte of the VBR is
also forced to zero. The VBR can be used to relocate the exception vector table from its default position
in the flash memory (address 0x(00)00_0000) to the base of the RAM (address 0x(00)80_0000) if needed.
Field
7–5
X
N
Z
V
C
4
3
2
1
0
Reset 0 0 0 0 0 0 0 0 – – – – – – – – – – – – – – – – – – – – – – – –
BDM: Load: 0xEF (PC)
Reserved, must be cleared.
Extend condition code bit. Set to the C-bit value for arithmetic operations; otherwise not affected or set to a specified
result.
Negative condition code bit. Set if most significant bit of the result is set; otherwise cleared.
Zero condition code bit. Set if result equals zero; otherwise cleared.
Overflow condition code bit. Set if an arithmetic overflow occurs implying the result cannot be represented in operand
size; otherwise cleared.
Carry condition code bit. Set if a carry out of the operand msb occurs for an addition or if a borrow occurs in a
subtraction; otherwise cleared.
W
R 0 0 0 0 0 0 0 0
Program Counter (PC)
Vector Base Register (VBR)
Store: 0xCF (PC)
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9
MCF51AC256 ColdFire Integrated Microcontroller Reference Manual, Rev. 5
Figure 7-6. Program Counter Register (PC)
Table 7-2. CCR Field Descriptions
Description
Address
8
7
Access: User read/write
6
Freescale Semiconductor
5
BDM read/write
4
3
2
1
0