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Section 6
Bus Controller (BSC)
Rev.2.00 Jun. 28, 2007 Page 201 of 666
REJ09B0311-0200
(2)
Write after Read
If an external write occurs after an external read while bit IDLS0 in IDLCRis set to 1, idle cycles
specified by bits IDLCA1 and IDLCA0 when bit IDSELn in IDLCR is cleared to 0 when
IDLSELn = 0,or bits IDLCB1 and IDLCB0 when IDLSELn is set to 1 are inserted at the start of
the write cycle (n = 0 to 7).
Figure 6.35 shows an example of the operation in this case. In this example, bus cycle A is a read
cycle for ROM with a long output floating time, and bus cycle B is a CPU write cycle. In (a), an
idle cycle is not inserted, and a conflict occurs in bus cycle B between the read data from ROM
and the CPU write data. In (b), an idle cycle is inserted, and a data conflict is prevented.
Data hold time is long.
Data conflict
Bus cycle A
Bus cycle B
B
φ
Address bus
CS
(area A)
CS
(area B)
RD
LLWR
Data bus
T
1
T
2
T
3
T
1
T
2
(b) Idle cycle inserted
Bus cycle A
Bus cycle B
T
1
T
2
T
3
T
1
T
i
T
2
(a) No idle cycle inserted
(IDLS0 = 0)
(IDLS0 = 1, IDLSELn = 0, IDLCA1 = 0, IDLCA0 = 0)
Figure 6.35 Example of Idle Cycle Operation (Write after Read)
Summary of Contents for H8SX/1650
Page 2: ...Rev 2 00 Jun 28 2007 Page ii of xxii...
Page 106: ...Section 4 Exception Handling Rev 2 00 Jun 28 2007 Page 84 of 666 REJ09B0311 0200...
Page 142: ...Section 5 Interrupt Controller Rev 2 00 Jun 28 2007 Page 120 of 666 REJ09B0311 0200...
Page 326: ...Section 8 I O Ports Rev 2 00 Jun 28 2007 Page 304 of 666 REJ09B0311 0200...
Page 470: ...Section 12 Watchdog Timer WDT Rev 2 00 Jun 28 2007 Page 448 of 666 REJ09B0311 0200...
Page 566: ...Section 14 A D Converter Rev 2 00 Jun 28 2007 Page 544 of 666 REJ09B0311 0200...
Page 574: ...Section 16 RAM Rev 2 00 Jun 28 2007 Page 552 of 666 REJ09B0311 0200...
Page 584: ...Section 17 Clock Pulse Generator Rev 2 00 Jun 28 2007 Page 562 of 666 REJ09B0311 0200...
Page 638: ...Section 19 List of Registers Rev 2 00 Jun 28 2007 Page 616 of 666 REJ09B0311 0200...
Page 668: ...Section 20 Electrical Characteristics Rev 2 00 Jun 28 2007 Page 646 of 666 REJ09B0311 0200...
Page 676: ...Appendix Rev 2 00 Jun 28 2007 Page 654 of 666 REJ09B0311 0200...
Page 688: ...Rev 2 00 Jun 28 2007 Page 666 of 666 REJ09B0311 0200...
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Page 692: ...H8SX 1650 Group Hardware Manual...