M16C6K9 Datasheet, PDF (195/292 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

M16C/6K9 Group
MULTI-MASTER I²C-BUS Interface
I²C control register 2
I²C0, 1 control register 2 (address: 032716, 033716, 031716) control the detection of communication abnormal-
ity. In I²C-BUS communication, the data transfer is controlled by the SCL clock signal. The devices will stop in
the communication state if SCL stops during transfer. So if the SCL clock stops in “H” state for a period of time,
the I²C-BUS interface circuit can detect the time out and request an I²C interrupt. Please see Fig.GC-12.
SCL
SDA
BB flag
Internal counter start signal
Internal counter stop, reset signal
Internal counter overflow signal
I²C interrupt request signal
1 clock
1 bit
2 clock
2 bit
3 clock
3 bit
SCL clock stop (“H”)
The time of timeout detection
Fig.GC-12 The timing of timeout detection
•Bit0: Time out detection function enable bit (TOE)
The bit enables timeout detection function. By setting this bit to “1”, the I²C interrupt request signal will be
generated if the SCL clock stops in “H” state for a period of time during bus busy (BB flag =“1”).
The time of time out detection which is selected by timeout detection time selection bit (TOSEL) with long
time mode or short time mode will be calculated by internal counter. When time out is detected, please set “0”
to I²C-BUS interface enable bit (ES0) and then process initialization.
•Bit1: Time out detection flag (TOF )
The bit is the flag showing timeout detection status. If the time which is calculated by the internal counter
overflows, the time out detection flag (TOF) becomes to “1”, and at the same time the I²C interrupt request
signal is generated.
•Bit2: timeout detection time selection bit (TOSEL)
The bit selects timeout detection time from long time and short time mode. If TOSEL = “0”, the long time
mode; TOSEL = “1”, the short mode is selected respectively. The long time is up counted by 16 bits counter
and the short time is up counted by 14 bits counter based on I²C system clock (VIIC). Table GC-7 shows
examples of the timeout detection time.
Table.GC-7 Examples of timeout detection time
VIIC(MHz)
Long time mode
4
16.4
2
32.8
1
65.6
(Unit: ms)
Short time mode
4.1
8.2
16.4
Rev.1.00 Jun 06, 2003 page 195 of 290