MC68EC000EI16 Freescale Semiconductor, MC68EC000EI16 Datasheet - Page 14

• Manufacturer Part Number: MC68EC000EI16
• Description: IC MPU 32BIT 16MHZ 68-PLCC
• Manufacturer: Freescale Semiconductor

Specifications of MC68EC000EI16

• Processor Type: M680x0 32-Bit
• Speed: 16MHz
• Voltage: 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 68-PLCC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -

1.1.3 Program Counter
The PC contains the address of the instruction currently executing. During instruction
execution and exception processing, the processor automatically increments the contents
or places a new value in the PC. For some addressing modes, the PC can be used as a
pointer for PC relative addressing.
1.1.4 Condition Code Register
Consisting of five bits, the CCR, the status register’s lower byte, is the only portion of the
status register (SR) available in the user mode. Many integer instructions affect the CCR,
indicating the instruction’s result. Program and system control instructions also use certain
combinations of these bits to control program and system flow. The condition codes meet
two criteria: consistency across instructions, uses, and instances and meaningful results
with no change unless it provides useful information.
Consistency across instructions means that all instructions that are special cases of more
general instructions affect the condition codes in the same way. Consistency across uses
means that conditional instructions test the condition codes similarly and provide the same
results whether a compare, test, or move instruction sets the condition codes. Consistency
across instances means that all instances of an instruction affect the condition codes in the
same way.
The first four bits represent a condition of the result generated by an operation. The fifth bit
or the extend bit (X-bit) is an operand for multiprecision computations. The carry bit (C-bit)
and the X-bit are separate in the M68000 family to simplify programming techniques that use
them (refer to Table 3-18 as an example). In the instruction set definitions, the CCR is
illustrated as follows:
MOTOROLA
X—Extend
N—Negative
Z—Zero
V—Overflow
Set to the value of the C-bit for arithmetic operations; otherwise not affected or set to a
Set if the most significant bit of the result is set; otherwise clear.
Set if the result equals zero; otherwise clear.
Set if an arithmetic overflow occurs implying that the result cannot be represented in the
specified result.
operand size; otherwise clear.
M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL
X
N
Z
V
C
Introduction
1-3