TSC80251 TEMIC [TEMIC Semiconductors], TSC80251 Datasheet - Page 27

• Manufacturer Part Number: TSC80251
• Manufacturer: TEMIC [TEMIC Semiconductors]

TSC80251
4.1.1. Selecting Binary Mode or Source Mode
If you have code that was written for a C51 microcontroller and you want to run it unmodified on a C251
microcontroller, choose binary mode. You can use the object code without reassembling the source code. You can also
assemble the source code with an assembler for the C251 Architecture and have it produce object code that is
binary–compatible with C51 microcontrollers. The remainder of this section discusses the selection of binary mode
or source mode for code that may contain instructions from both architectures.
An instruction with a prefixed opcode requires one more byte for code storage, and if an additional fetch is required
for the extra byte, the execution time is increased by one state. This means that using fewer prefixed opcodes produces
more efficient code.
If a program uses only instructions from the C51 Architecture, the binary–mode code is more efficient because it uses
no prefixes. On the other hand, if a program uses many more new instructions than instructions from the C51
Architecture , source mode is likely to produce more efficient code. For a program where the choice is not clear, the
better mode can be found by experimenting with a simulator.
4.2. Programming Features of the C251 Architecture
The instruction set for TSC80251 microcontrollers provides the user with new instructions that exploit the features of
the C251 Architecture while maintaining compatibility with the instruction set for 80C51 microcontrollers. Many of
the new instructions can operate on either 8–bit (byte), 16–bit (word) or 32–bit (dword) operands (In comparison with
8–bit and 16–bit operands, 32–bit operands are accessed with fewer addressing modes.). This capability increases the
ease and efficiency of programming TSC80251 microcontrollers in a high–level language such as C.
The instruction set is divided into “Data Instructions”, “Bit Instructions” and “Control Instructions”. Data instructions
process 8–bit, 16–bit and 32–bit data; bit instructions manipulate bits; and control instructions manage program flow.
4.2
0H
FH
0H
FH
0H
0H
C51 Architecture
C51 Architecture
I
I
Figure 4.1. Binary Mode Opcode Map
Figure 4.2. Source Mode Opcode Map
5H
5H
6H
6H
C251 Architecture
C51 Architecture
II
III
FH
FH
0H
FH
0H
FH
6H
6H
C251 Architecture
C51 Architecture
A5H Prefix
A5H Prefix
III
II
FH
FH
Rev. C – May 7, 1999