SH7751 Group, SH7751R Group
Appendix F Instruction Prefetching and Its Side Effects
R01UH0457EJ0301 Rev. 3.01
Page 1119 of 1128
Sep 24, 2013
Appendix F Instruction Prefetching and Its Side Effects
The SH7751 Group is provided with an internal buffer for holding pre-read instructions, and
always performs pre-reading. Therefore, program code must not be located in the last 20-byte area
of any memory space. If program code is located in these areas, the memory area will be exceeded
and a bus access for instruction pre-reading may be initiated. A case in which this is a problem is
shown below.
Address
H'03FFFFF8
H'03FFFFFA
H'03FFFFFC
H'03FFFFFE
H'04000000
H'04000002
Area 0
Area 1
ADD R1,R4
JMP @R2
NOP
NOP
.
.
.
.
.
PC (pro
g
ram counter)
Instruction prefetch address
Figure F.1 Instruction Prefetch
Figure F.1 presupposes a case in which the instruction (ADD) indicated by the program counter
(PC) and the address H'04000002 instruction prefetch are executed simultaneously. It is also
assumed that the program branches to an area other than area 1 after executing the following JMP
instruction and delay slot instruction.
In this case, the program flow is unpredictable, and a bus access (instruction prefetch) to area 1
may be initiated.
Instruction Prefetch Side Effects
1. It is possible that an external bus access caused by an instruction prefetch may result in
misoperation of an external device, such as a FIFO, connected to the area concerned.
2. If there is no device to reply to an external bus request caused by an instruction prefetch,
hangup will occur.
Remedies
1. These illegal instruction fetches can be avoided by using the MMU.
2. The problem can be avoided by not locating program code in the last 20 bytes of any area.
Содержание SH7751 Group
Страница 2: ...Page ii of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 30: ...Page xxx of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 46: ...Page xlvi of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 54: ...Page liv of liv R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 190: ...Section 4 Caches SH7751 Group SH7751R Group Page 136 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 226: ...Section 5 Exceptions SH7751 Group SH7751R Group Page 172 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 264: ...Section 7 Instruction Set SH7751 Group SH7751R Group Page 210 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 320: ...Section 9 Power Down Modes SH7751 Group SH7751R Group Page 266 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 344: ...Section 10 Clock Oscillation Circuits SH7751 Group SH7751R Group Page 290 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 388: ...Section 12 Timer Unit TMU SH7751 Group SH7751R Group Page 334 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 800: ...Section 17 Smart Card Interface SH7751 Group SH7751R Group Page 746 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 848: ...Section 19 Interrupt Controller INTC SH7751 Group SH7751R Group Page 794 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 876: ...Section 20 User Break Controller UBC SH7751 Group SH7751R Group Page 822 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 1036: ...Section 22 PCI Controller PCIC SH7751 Group SH7751R Group Page 982 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 1152: ...Appendix C Mode Pin Settings SH7751 Group SH7751R Group Page 1098 of 1128 R01UH0457EJ0301 Rev 3 01 Sep 24 2013 ...
Страница 1185: ......
Страница 1186: ... SH7751 Group SH7751R Group User s Manual Hardware R01UH0457EJ0301 Previous Number REJ09B0370 0400 ...