390
CHAPTER 18 SERIAL INTERFACE CHANNEL 0 (
µ
PD78078Y Subseries)
18.4.4 I
2
C bus mode operation
The I
2
C bus mode is provided for when communication operations are performed between a single master device
and multiple slave devices. This mode configures a serial bus that includes only a single master device, and is
based on the clocked serial I/O format with the addition of bus configuration functions, which allows the master
device to communicate with a number of (slave) devices using only two lines: serial clock (SCL) line and serial data
bus (SDA0 or SDA1) line. Consequently, when the user plans to configure a serial bus which includes multiple
microcontrollers and peripheral devices, using this configuration results in reduction of the required number of port
pins and on-board wires.
In the I
2
C bus specification, the master sends start condition, data, and stop condition signals to slave devices
through the serial data bus, while slave devices automatically detect and distinguish the type of signals due to the
signal detection function incorporated as hardware. This simplifies the application program to control I
2
C bus.
An example of a serial bus configuration is shown in Figure 18-13. This system below is composed of CPUs and
peripheral ICs having serial interface hardware that complies with the I
2
C bus specification.
Note that pull-up resistors are required to connect to both serial clock line and serial data bus line, because open-
drain buffers are used for the serial clock pin (SCL) and the serial data bus pin (SDA0 or SDA1) on the I
2
C bus.
The signals used in the I
2
C bus mode are described in Table 18-4.
Figure 18-13. Example of Serial Bus Configuration Using I
2
C Bus
SCL
SDA0 (SDA1)
SCL
SDA0 (SDA1)
SCL
SDA0 (SDA1)
SCL
SDA
Slave IC
Slave CPU2
Slave CPU1
Master CPU
V
DD
Serial clock
Serial data bus
V
DD
Summary of Contents for PD78076
Page 2: ...2 MEMO ...
Page 12: ...12 MEMO ...
Page 48: ...48 MEMO ...
Page 64: ...64 MEMO ...
Page 82: ...82 MEMO ...
Page 100: ...100 MEMO ...
Page 130: ...130 MEMO ...
Page 180: ...180 MEMO ...
Page 222: ...222 MEMO ...
Page 248: ...248 MEMO ...
Page 288: ...288 MEMO ...
Page 308: ...308 MEMO ...
Page 364: ...364 MEMO ...
Page 494: ...494 MEMO ...
Page 526: ...526 MEMO ...
Page 544: ...544 MEMO ...
Page 558: ...558 MEMO ...
Page 580: ...580 MEMO ...
Page 596: ...596 MEMO ...
Page 598: ...598 MEMO ...
Page 626: ...626 MEMO ...