Register Descriptions; C Bus Data Register (Icdr) - Renesas H8S Series Hardware Manual

2
Section 16 I C Bus Interface (IIC)
16.3

Register Descriptions

2
The I C bus interface has the following registers. Registers ICDR and SARX and registers ICMR
and SAR are allocated to the same addresses. Accessible registers differ depending on the ICE bit
in ICCR. When the ICE bit is cleared to 0, SAR and SARX can be accessed, and when the ICE bit
is set to 1, ICMR and ICDR can be accessed. For details on the serial timer control register, see
section 3.2.3, Serial Timer Control Register (STCR).
• I
2
C bus control register (ICCR)
• I
2
C bus status register (ICSR)
• I
2

C bus data register (ICDR)

• I
2
C bus mode register (ICMR)
• Slave address register (SAR)
• Second slave address register (SARX)
• I
2
C bus extended control register (ICXR)
• DDC switch register (DDCSWR)*
Note: DDCSWR is available in IIC_0.
2
16.3.1 I C Bus Data Register (ICDR)
ICDR is an 8-bit readable/writable register that is used as a transmit data register when
transmitting and a receive data register when receiving. ICDR is internally divided into a shift
register (ICDRS), receive buffer (ICDRR), and transmit buffer (ICDRT). Data transfers among
these three registers are performed automatically in accordance with changes in the bus state, and
they affect the status of internal flags such as ICDRE and ICDRF.
In master transmit mode with the I
performed after start condition detection. When the start condition is detected, previous write data
is ignored. In slave transmit mode, writing should be performed after the slave addresses match
and the TRS bit is automatically changed to 1.
If the IIC is in transmit mode (TRS = 1) and ICDRT has the next data (the ICDRE flag is 0), data
is transferred automatically from ICDRT to ICDRS, following transmission of one frame of data
using ICDRS. When the ICDRE flag is 1 and the next transmit data writing is waited, data is
transferred automatically from ICDRT to ICDRS by writing to ICDR. If I
(TRS = 0), no data is transferred from ICDRT to ICDRS. Note that data should not be written to
ICDR in receive mode.
Reading receive data from ICDR is performed after data is transferred from ICDRS to ICDRR.
Rev. 3.00 Jul. 14, 2005 Page 510 of 986
REJ09B0098-0300
2
C bus format, writing transmit data to ICDR should be
2
C is in receive mode