COP8AME9_14 Datasheet, PDF (86/102 Pages) Texas Instruments – COP8AME9 8-Bit CMOS Flash Microcontroller with 8k Memory, Dual Op Amps, Virtual EEPROM, Temperature Sensor, 10-Bit A/D and Brownout Reset

COP8AME9, COP8ANE9
SNOS930F – MARCH 2001 – REVISED MARCH 2013
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Tranfer-of-Control Addressing Modes
Program instructions are usually executed in sequential order. However, Jump instructions can be used to
change the normal execution sequence. Several transfer-of-control addressing modes are available to specify
jump addresses.
A change in program flow requires a non-incremental change in the Program Counter contents. The Program
Counter consists of two bytes, designated the upper byte (PCU) and lower byte (PCL). The most significant bit of
PCU is not used, leaving 15 bits to address the program memory.
Different addressing modes are used to specify the new address for the Program Counter. The choice of
addressing mode depends primarily on the distance of the jump. Farther jumps sometimes require more
instruction bytes in order to completely specify the new Program Counter contents.
The available transfer-of-control addressing modes are:
• Jump Relative
• Jump Absolute
• Jump Absolute Long
• Jump Indirect
The transfer-of-control addressing modes are described below. Each description includes an example of a Jump
instruction using a particular addressing mode, and the effect on the Program Counter bytes of executing that
instruction.
Jump Relative. In this 1-byte instruction, six bits of the instruction opcode specify the distance of the jump from
the current program memory location. The distance of the jump can range from −31 to +32. A JP+1 instruction is
not allowed. The programmer should use a NOP instead.
Example: Jump Relative
JP 0A
Reg
PCU
PCL
Contents
Before
02 Hex
05 Hex
Contents
After
02 Hex
0F Hex
Jump Absolute. In this 2-byte instruction, 12 bits of the instruction opcode specify the new contents of the
Program Counter. The upper three bits of the Program Counter remain unchanged, restricting the new Program
Counter address to the same 4k-byte address space as the current instruction. (This restriction is relevant only in
devices using more than one 4k-byte program memory space.)
Example: Jump Absolute
JMP 0125
Reg
PCU
PCL
Contents
Before
0C Hex
77 Hex
Contents
After
01 Hex
25 Hex
Jump Absolute Long. In this 3-byte instruction, 15 bits of the instruction opcode specify the new contents of the
Program Counter.
Example: Jump Absolute Long
JMP 03625
Reg/
Memory
PCU
PCL
Contents
Before
42 Hex
36 Hex
Contents
After
36 Hex
25 Hex
86
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