CHAPTER 3 REGISTERS
3.3.1How To Use The Temporary Accumulator (T)
The F2MC-8FX CPU has a special-purpose register called a temporary accumulator. This section described the operation of this register.
■How to Use the Temporary Accumulator (T)
The F2MC-8FX CPU has various binary operation instructions, some data transfer instructions and the temporary accumulator (T) for 16-bit data operation. Although there is no instruction for direct data transfer to the temporary accumulator, the value of the original accumulator is transferred to the temporary accumulator before executing the instruction for data transfer to the accumulator. Therefore, to perform operations between the accumulator and temporary accumulator, execute operations after carrying out the instruction for data transfer to the accumulator twice. Since data is not automatically transferred by all instructions to the temporary accumulator, see the columns of TL and TH in the instruction list for details of actual data transfer instructions. An example of addition with carry of 16-bit data stored at addresses 1280H and 0042H is shown below.
MOVW A, 0042H | - |
MOVW A, 1280H | - |
ADDCW A | - |
Figure 3.3-7shows the operation for the accumulator and temporary accumulator when the above example is executed.
Figure 3.3-7 Operation of Accumulator (A) and Temporary Accumulator (T) in Word Data Processing
Before execution | | | | | | | | | Last result |
A | XXXXH | A | 1234H | A | 5678H | | + | A | 68ACH | |
T | XXXXH | T | XXXXH | T | 1234H | CF | 0 | T | 1234H | |
| | RAM | | | RAM | | | RAM | | | | RAM | |
1281H | 78H | 1281H | 78H | 1281H | | 78H | | | 1281H | 78H | |
1280H | 56H | 1280H | 56H | 1280H | | 56H | | | 1280H | 56H | |
| ... | ... | | ... | ... | ... | ... | | | ... | ... |
0043H | 34H | 0043H | 34H | 0043H | 34H | | | 0043H | 34H | |
0042H | 12H | 0042H | 12H | 0042H | | 12H | | | 0042H | 12H | |
