CONNECTION WITH EXTERNAL DEVICES
12.1 Signals required for accessing external devices
7751 Group User’s Manual
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12.1.2 Operation of bus interface unit (BIU)
Figures 12.1.5 and 12.1.6 show the examples of operating waveforms of the signals input and output to
/from externals when accessing external devices. The following explains these waveforms compared with
the basic operating waveform (refer to section “2.2.3 Operation of bus interface unit (BIU).”)
(1)
When fetching instructions into instruction queue buffer
➀
When the instruction which is next fetched is located at an even address in the 16-bit external data
bus width, the BIU fetches 2 bytes at a time with the waveform (a). When in the 8-bit external data
bus width, the BIU fetches only 1 byte with the first half of waveform (e).
➁
When the instruction which is next fetched is located at an odd address in the 16-bit external data
bus width, the BIU fetches only 1 byte with the waveform (d). When in the 8-bit external data bus
width, the BIU fetches only 1 byte with the first half of waveform (f).
When a branch to an odd address is caused by a branch instruction and others in the 16-bit external
data bus width, the BIU first fetches 1 byte in waveform (d), and after that, fetches each two bytes
at a time in waveform (a).
(2)
When reading or writing data to and from memory•I/O device
➀
When accessing 16-bit data which begins at an even address, waveform (a) or (e) is applied.
➁
When accessing 16-bit data which begins at an odd address, waveform (b) or (f) is applied.
➂
When accessing 8-bit data at an even address, waveform (c) or the first half of (e) is applied.
➃
When accessing 8-bit data at an odd address, waveform (d) or the first half of (f) is applied.
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.”
The setup of flags m and x and the selection of the external data bus width do not affect each other.
Summary of Contents for 7700 FAMILY
Page 2: ...MITSUBISHI 16 BIT SINGLE CHIP MICROCOMPUTER 7700 FAMILY 7751 SERIES 7751 Group User s Manual...
Page 11: ...Table of Contents viii 7751 Group User s Manual MEMORANDUM...
Page 157: ...TIMER B 6 28 7751 Group User s Manual 6 5 Pulse period pulse width measurement mode MEMORANDUM...
Page 245: ...7751 Group User s Manual 8 36 A D CONVERTER Precautions when using A D converter MEMORANDUM...
Page 265: ...7751 Group User s Manual WAIT MODE 11 6 11 3 Precautions for Wait mode MEMORANDUM...
Page 289: ...CONNECTION WITH EXTERNAL DEVICES 12 4 Hold function 7751 Group User s Manual 12 24 MEMORANDUM...
Page 290: ...CHAPTER 13 RESET 13 1 Hardware reset 13 2 Software reset...
Page 302: ...CHAPTER 14 CLOCK GENERATING CIRCUIT 14 1 Oscillation circuit example 14 2 Clock...
Page 307: ...CLOCK GENERATING CIRCUIT 7751 Group User s Manual 14 6 14 2 Clock MEMORANDUM...
Page 360: ...CHAPTER 16 STANDARD CHARACTERISTICS 16 1 Standard characteristics...
Page 366: ...CHAPTER 17 APPLICATIONS 17 1 Memory expansion...
Page 405: ...APPLICATIONS 7751 Group User s Manual 17 40 17 1 Memory expansion MEMORANDUM...
Page 406: ...CHAPTER 18 PROM VERSION 18 1 EPROM mode 18 2 Usage precaution...
Page 417: ...7751 Group User s Manual PROM VERSION 18 12 18 2 Usage precaution MEMORANDUM...
Page 418: ...CHAPTER 19 FLASH MEMORY VERSION 19 1 Parallel input output mode 19 2 Serial input output mode...
Page 451: ...FLASH MEMORY VERSION 7751 Group User s Manual 19 34 19 2 Serial input output mode MEMORANDUM...
Page 484: ...APPENDIX 7751 Group User s Manual 20 33 Appendix 4 Package outlines 80D0...
Page 489: ...APPENDIX 7751 Group User s Manual 20 38 Appendix 6 Hexadecimal instruction code table...
Page 490: ...APPENDIX 7751 Group User s Manual 20 39 Appendix 6 Hexadecimal instruction code table...
Page 492: ...APPENDIX 7751 Group User s Manual 20 41 Appendix 7 Machine instructions...
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Page 535: ...APPENDIX Appendix 9 Q A 7751 Group User s Manual 20 84 MEMORANDUM...
Page 536: ...GLOSSARY...
Page 539: ...GLOSSARY 7751 Group User s Manual 4 MEMORANDUM...