CENTRAL PROCESSING UNIT (CPU)
7751 Group User’s Manual
2–15
2.2 Bus interface unit
2.2.3 Operation of bus interface unit (BIU)
Figure 2.2.3 shows the basic operating waveforms of the bus interface unit (BIU).
About signals which are input/output externally when accessing external devices, refer to “Chapter 12.
CONNECTION WITH EXTERNAL DEVICES.”
(1)
When fetching instructions into the instruction queue buffer
➀
When the instruction which is next fetched is located at an even address, the BIU fetches 2 bytes
at a time with the timing of waveform (a).
However, when accessing an external device which is connected with the 8-bit external data bus
width (BYTE = “H”), only 1 byte is fetched.
➁
When the instruction which is next fetched is located at an odd address, the BIU fetches only 1
byte with the timing of waveform (a). The contents at the even address are not taken.
(2)
When reading or writing data to and from the memory•I/O device
➀
When accessing a 16-bit data which begins at an even address, waveform (a) is applied. The 16
bits of data are accessed at a time.
➁
When accessing a 16-bit data which begins at an odd address, waveform (b) is applied. The 16
bits of data are accessed separately in 2 operations, 8 bits at a time. Invalid data is not fetched
into the data buffer.
➂
When accessing an 8-bit data at an even address, waveform (a) is applied. The data at the odd
address is not fetched into the data buffer.
➃
When accessing an 8-bit data at an odd address, waveform (a) is applied. The data at the even
address is not fetched into the data buffer.
For instructions that are affected by the data length flag (m) and the index register length flag (x),
operation
➀
or
➁
is applied when flag m or x = “0”; operation
➂
or
➃
is applied when flag m or x
= “1.”
Содержание 7700 FAMILY
Страница 2: ...MITSUBISHI 16 BIT SINGLE CHIP MICROCOMPUTER 7700 FAMILY 7751 SERIES 7751 Group User s Manual...
Страница 11: ...Table of Contents viii 7751 Group User s Manual MEMORANDUM...
Страница 12: ...CHAPTER 1 DESCRIPTION 1 1 Performance overview 1 2 Pin configuration 1 3 Pin description 1 4 Block diagram...
Страница 48: ...CHAPTER 3 INPUT OUTPUT PINS 3 1 Programmable I O ports 3 2 I O pins of internal peripheral devices...
Страница 157: ...TIMER B 6 28 7751 Group User s Manual 6 5 Pulse period pulse width measurement mode MEMORANDUM...
Страница 245: ...7751 Group User s Manual 8 36 A D CONVERTER Precautions when using A D converter MEMORANDUM...
Страница 246: ...CHAPTER 9 WATCHDOG TIMER 9 1 Block description 9 2 Operation description 9 3 Precautions when using watchdog timer...
Страница 254: ...CHAPTER 10 STOP MODE 10 1 Clock generating circuit 10 2 Operation description 10 3 Precautions for Stop mode...
Страница 260: ...CHAPTER 11 WAIT MODE 11 1 Clock generating circuit 11 2 Operation description 11 3 Precautions for Wait mode...
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Страница 289: ...CONNECTION WITH EXTERNAL DEVICES 12 4 Hold function 7751 Group User s Manual 12 24 MEMORANDUM...
Страница 290: ...CHAPTER 13 RESET 13 1 Hardware reset 13 2 Software reset...
Страница 302: ...CHAPTER 14 CLOCK GENERATING CIRCUIT 14 1 Oscillation circuit example 14 2 Clock...
Страница 307: ...CLOCK GENERATING CIRCUIT 7751 Group User s Manual 14 6 14 2 Clock MEMORANDUM...
Страница 359: ...ELECTRICAL CHARACTERISTICS 7751 Group User s Manual 15 52 MEMORANDUM 15 15 Testing circuit for ports P0 to P8 1 and E...
Страница 360: ...CHAPTER 16 STANDARD CHARACTERISTICS 16 1 Standard characteristics...
Страница 365: ...STANDARD CHARACTERISTICS 16 1 Standard characteristics 7751 Group User s Manual 16 6 MEMORANDUM...
Страница 366: ...CHAPTER 17 APPLICATIONS 17 1 Memory expansion...
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Страница 406: ...CHAPTER 18 PROM VERSION 18 1 EPROM mode 18 2 Usage precaution...
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Страница 418: ...CHAPTER 19 FLASH MEMORY VERSION 19 1 Parallel input output mode 19 2 Serial input output mode...
Страница 451: ...FLASH MEMORY VERSION 7751 Group User s Manual 19 34 19 2 Serial input output mode MEMORANDUM...
Страница 483: ...APPENDIX 7751 Group User s Manual 20 32 Appendix 4 Package outlines Appendix 4 Package outlines 80P6N A...
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Страница 489: ...APPENDIX 7751 Group User s Manual 20 38 Appendix 6 Hexadecimal instruction code table...
Страница 490: ...APPENDIX 7751 Group User s Manual 20 39 Appendix 6 Hexadecimal instruction code table...
Страница 491: ...APPENDIX 7751 Group User s Manual 20 40 Appendix 7 Machine instructions Appendix 7 Machine instructions...
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Страница 536: ...GLOSSARY...
Страница 539: ...GLOSSARY 7751 Group User s Manual 4 MEMORANDUM...