Module Stop Mode Setting - Renesas H8S/2100 Series Hardware Manual

6. Note on ICDR read in transmit mode and ICDR write in receive mode
If ICDR is read in transmit mode (TRS = 1) or ICDR is written to in receive mode (TRS = 0),
the SCL pin may not be held low in some cases after transmit/receive operation has been
completed, thus inconveniently allowing clock pulses to be output on the SCL bus line before
ICDR is accessed correctly. To access ICDR correctly, read ICDR after setting receive mode
or write to ICDR after setting transmit mode.
7. Note on ACKE and TRS bits in slave mode
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In the I C bus interface, if 1 is received as the acknowledge bit value (ACKB = 1) in transmit
mode (TRS = 1) and then the address is received in slave mode without performing appropriate
processing, interrupt handling may start at the rising edge of the 9th clock pulse even when the
address does not match. Similarly, if the start condition or address is transmitted from the
master device in slave transmit mode (TRS = 1), the IRIC flag may be set after the ICDRE flag
is set and 1 received as the acknowledge bit value (ACKB = 1), thus causing an interrupt
source even when the address does not match.
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To use the I C bus interface module in slave mode, be sure to follow the procedures below.
A. When having received 1 as the acknowledge bit value for the last transmit data at the end
of a series of transmit operation, clear the ACKE bit in ICCR once to initialize the ACKB
bit to 0.
B. Set receive mode (TRS = 0) before the next start condition is input in slave mode.
Complete transmit operation by the procedure shown in figure 18.16, in order to switch
from slave transmit mode to slave receive mode.
18.6.1

Module Stop Mode Setting

The IIC operation can be enabled or disabled using the module stop control register. The initial
setting is for the IIC operation to be halted. Register access is enabled by canceling module stop
mode. For details, see section 26, Power-Down Modes.
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Section 18 I C Bus Interface (IIC)
Rev. 1.00 Apr. 28, 2008 Page 585 of 994
REJ09B0452-0100