
39
CHAPTER 2 CPU
2.7.1
Accumulator (A)
The accumulator (A) register consists of two 16-bit arithmetic operation registers (AH
and AL), and is used as a temporary storage for operation results and transfer data.
■
Accumulator (A)
The A register consists of two 16-bit arithmetic operation registers (AH and AL). The A register is used as
a temporary storage for operation results and transfer data. During 32-bit data processing, AH and AL are
used together. Only AL is used for word processing in 16-bit data processing mode or for byte processing
in 8-bit data processing mode (see Figure 2.7-3 and Figure 2.7-4). The data stored in the A register can be
operated upon with the data in memory or registers (Ri, RWi, or RLi). In the same manner as with the
F
2
MC-8L, when a word or shorter data item is transferred to AL, the previous data item in AL is
automatically sent to AH (data preservation function). The data preservation function and operation
between AL and AH help improve processing efficiency.
When a byte or shorter data item is transferred to AL, the data is sign-extended or zero-extended and stored
as a 16-bit data item in AL. The data in AL can be handled either as word or byte long.
When a byte-processing arithmetic operation instruction is executed on AL, the high-order eight bits of AL
before operation are ignored. The high-order eight bits of the operation result all become zeroes.
The A register is not initialized by a reset. The A register holds an undefined value immediately after a
reset.
Figure 2.7-3 32-bit Data Transfer
Figure 2.7-4 AL-AH Transfer
XXXXH
XXXXH
8F74H
2B52H
DTB
A6H
+6
RW1
A61540H
A6153EH
MSB
LSB
8FH
2BH
15H
74H
52H
38H
AH
AL
MOVL A,@R
W1+6
Old A
New A
+6
RW1
A61540H
A6153EH
XXXX H
1234H
1234H
1234H
DTB
A6H
8FH
2BH
15H
74H
52H
38H
MSB
LSB
MOVW A,@R
W1+6
Old A
New A
Summary of Contents for MB90390 Series
Page 2: ......
Page 4: ......
Page 17: ...xiii APPENDIX D List of Interrupt Vectors 690 INDEX 695 ...
Page 18: ...xiv ...
Page 132: ...104 CHAPTER 5 CLOCKS ...
Page 152: ...124 CHAPTER 6 CLOCK MODULATOR ...
Page 210: ...182 CHAPTER 11 TIME BASE TIMER ...
Page 218: ...190 CHAPTER 12 WATCHDOG TIMER ...
Page 264: ...236 CHAPTER 14 16 BIT RELOAD TIMER WITH EVENT COUNT FUNCTION ...
Page 274: ...246 CHAPTER 15 WATCH TIMER ...
Page 306: ...278 CHAPTER 17 DTP EXTERNAL INTERRUPTS ...
Page 338: ...310 CHAPTER 18 8 10 BIT A D CONVERTER ...
Page 364: ...336 CHAPTER 19 UART0 UART1 ...
Page 398: ...370 CHAPTER 20 UART2 UART3 Figure 20 5 2 ORE Set Timing Receive data RDRF ORE ...
Page 432: ...404 CHAPTER 20 UART2 UART3 ...
Page 482: ...454 CHAPTER 22 SERIAL I O ...
Page 560: ...532 CHAPTER 24 STEPPING MOTOR CONTROLLER ...
Page 582: ...554 CHAPTER 27 ROM MIRRORING MODULE ...
Page 632: ...604 CHAPTER 29 EXAMPLES OF SERIAL PROGRAMMING CONNECTION ...
Page 722: ...694 APPENDIX ...
Page 723: ...695 INDEX The index follows on the next page This is listed in alphabetic order ...
Page 740: ......