MC68HC908JK8CP Freescale Semiconductor, MC68HC908JK8CP Datasheet - Page 48

• Manufacturer Part Number: MC68HC908JK8CP
• Manufacturer: Freescale Semiconductor

Specifications of MC68HC908JK8CP

• Cpu Family: HC08
• Device Core Size: 8b
• Frequency (max): 8MHz
• Interface Type: SCI
• Program Memory Type: Flash
• Program Memory Size: 8KB
• Total Internal Ram Size: 256Byte
• # I/os (max): 15
• Number Of Timers - General Purpose: 4
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 13-chx8-bit
• Instruction Set Architecture: CISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Through Hole
• Pin Count: 20
• Package Type: PDIP
• Lead Free Status / Rohs Status: Not Compliant

Central Processor Unit (CPU)
4.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the
instruction just executed. Bits 6 and 5 are set permanently to logic 1. The following paragraphs describe
the functions of the condition code register.
V — Overflow Flag
H — Half-Carry Flag
I — Interrupt Mask
48
The CPU sets the overflow flag when a two's complement overflow occurs. The signed branch
instructions BGT, BGE, BLE, and BLT use the overflow flag.
The CPU sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an
add-without-carry (ADD) or add-with-carry (ADC) operation. The half-carry flag is required for
binary-coded decimal (BCD) arithmetic operations. The DAA instruction uses the states of the H and
C flags to determine the appropriate correction factor.
When the interrupt mask is set, all maskable CPU interrupts are disabled. CPU interrupts are enabled
when the interrupt mask is cleared. When a CPU interrupt occurs, the interrupt mask is set
automatically after the CPU registers are saved on the stack, but before the interrupt vector is fetched.
1 = Overflow
0 = No overflow
1 = Carry between bits 3 and 4
0 = No carry between bits 3 and 4
1 = Interrupts disabled
0 = Interrupts enabled
To maintain M6805 Family compatibility, the upper byte of the index
register (H) is not stacked automatically. If the interrupt service routine
modifies H, then the user must stack and unstack H using the PSHH and
PULH instructions.
Reset:
Reset:
Read:
Read:
Write:
Write:
MC68HC908JL8/JK8 • MC68HC08JL8/JK8 • MC68HC908KL8 Data Sheet, Rev. 3.1
X = Indeterminate
Bit
15
Bit 7
V
X
14
Figure 4-6. Condition Code Register (CCR)
13
6
1
1
Figure 4-5. Program Counter (PC)
12
11
Loaded with Vector from $FFFE and $FFFF
5
1
1
10
NOTE
9
H
4
X
8
7
3
1
I
6
5
N
X
2
4
3
X
1
Z
2
Freescale Semiconductor
1
Bit 0
C
X
Bit 0