Section 17 I
2
C Bus Interface (IIC)
Rev. 3.00 Jan 25, 2006 page 542 of 872
REJ09B0286-0300
5. The I
2
C bus interface specification for the SCL rise time t
sr
is 1000 ns or less (300 ns for high-
speed mode). In master mode, the I
2
C bus interface monitors the SCL line and synchronizes
one bit at a time during communication. If t
sr
(the time for SCL to go from low to V
IH
) exceeds
the time determined by the input clock of the I
2
C bus interface, the high period of SCL is
extended. The SCL rise time is determined by the pull-up resistance and load capacitance of
the SCL line. To insure proper operation at the set transfer rate, adjust the pull-up resistance
and load capacitance so that the SCL rise time does not exceed the values given in table 17.12.
Table 17.12 Permissible SCL Rise Time (t
sr
) Values
Time Indication[ns]
IICX1,
IICX0
t
cyc
Indication
I
2
C Bus
Specification
(Max.)
φφφφ
=
5 MHz
φφφφ
=
8 MHz
φφφφ
=
10 MHz
φφφφ
=
16 MHz
φφφφ
=
20 MHz
φφφφ
=
25 MHz
0
7.5 t
cyc
Standard mode
1000
1000
937
750
468
375
300
High-speed mode 300
300
300
300
300
300
300
1
17.5 t
cyc
Standard mode
1000
1000
1000
1000
1000
875
700
High-speed mode 300
300
300
300
300
300
300
6. The I
2
C bus interface specifications for the SCL and SDA rise and fall times are under 1000 ns
and 300 ns. The I
2
C bus interface SCL and SDA output timing is prescribed by t
cyc
, as shown
in table 17.11. However, because of the rise and fall times, the I
2
C bus interface specifications
may not be satisfied at the maximum transfer rate. Table 17.13 shows output timing
calculations for different operating frequencies, including the worst-case influence of rise and
fall times. The values in the above table will vary depending on the settings of the IICX1,
IICX0, and CKS2 to CKS0 bits. Depending on the frequency it may not be possible to achieve
the maximum transfer rate; therefore, whether or not the I
2
C bus interface specifications are
met must be determined in accordance with the actual setting conditions. t
BUFO
fails to meet the
I
2
C bus interface specifications at any frequency. The following solutions should be
investigated.
• Provide coding to secure the necessary interval (approximately 1 µs) between issuance of a
stop condition and issuance of a start condition.
• Select devices whose input timing permits this output timing for use as slave devices
connected to the I
2
C bus.
t
SCLLO
in high-speed mode and t
STASO
in standard mode fail to satisfy the I
2
C bus interface
specifications for worst-case calculations of t
Sr
/t
Sf
. The following solutions should be
investigated.
• Adjusting the rise and fall times by means of a pull-up resistor and capacitive load.
• Reducing the transfer rate to meet the specifications.
Содержание H8S/2158
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Страница 36: ...Rev 3 00 Jan 25 2006 page xxxiv of lii B Product Lineup 863 C Package Dimensions 864 Index 865...
Страница 47: ...Rev 3 00 Jan 25 2006 page xlv of lii Appendix Figure C 1 Package Dimensions TBP 112A 864...
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Страница 70: ...Section 1 Overview Rev 3 00 Jan 25 2006 page 16 of 872 REJ09B0286 0300...
Страница 118: ...Section 3 MCU Operating Modes Rev 3 00 Jan 25 2006 page 64 of 872 REJ09B0286 0300...
Страница 126: ...Section 4 Exception Handling Rev 3 00 Jan 25 2006 page 72 of 872 REJ09B0286 0300...
Страница 198: ...Section 6 Bus Controller Rev 3 00 Jan 25 2006 page 144 of 872 REJ09B0286 0300...
Страница 326: ...Section 10 8 Bit PWM Timer PWM Rev 3 00 Jan 25 2006 page 272 of 872 REJ09B0286 0300...
Страница 440: ...Section 15 Watchdog Timer WDT Rev 3 00 Jan 25 2006 page 386 of 872 REJ09B0286 0300...
Страница 606: ...Section 17 I 2 C Bus Interface IIC Rev 3 00 Jan 25 2006 page 552 of 872 REJ09B0286 0300...
Страница 742: ...Section 19 Multimedia Card Interface MCIF Rev 3 00 Jan 25 2006 page 688 of 872 REJ09B0286 0300...
Страница 744: ...Section 20 Encryption Operation Circuit DES and GF Rev 3 00 Jan 25 2006 page 690 of 872 REJ09B0286 0300...
Страница 750: ...Section 21 D A Converter Rev 3 00 Jan 25 2006 page 696 of 872 REJ09B0286 0300...
Страница 768: ...Section 22 A D Converter Rev 3 00 Jan 25 2006 page 714 of 872 REJ09B0286 0300...
Страница 770: ...Section 23 RAM Rev 3 00 Jan 25 2006 page 716 of 872 REJ09B0286 0300...
Страница 824: ...Section 26 Clock Pulse Generator Rev 3 00 Jan 25 2006 page 770 of 872 REJ09B0286 0300...
Страница 844: ...Section 27 Power Down Modes Rev 3 00 Jan 25 2006 page 790 of 872 REJ09B0286 0300...
Страница 878: ...Section 28 List of Registers Rev 3 00 Jan 25 2006 page 824 of 872 REJ09B0286 0300...
Страница 926: ...Index Rev 3 00 Jan 25 2006 page 872 of 872 REJ09B0286 0300...