NXP Semiconductors MC9S08LG16, Reference Manual

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Chapter 10 Inter-Integrated Circuit (S08IICV2)
MC9S08LG32 MCU Series, Rev. 5
250 Freescale Semiconductor
NOTE
When transitioning out of master receive mode, the IIC mode should be
switched before reading the IICxD register to prevent an inadvertent
initiation of a master receive data transfer.
In slave mode, the same functions are available after an address match has occurred.
The TX bit in IICxC must correctly reflect the desired direction of transfer in master and slave modes for
the transmission to begin. For instance, if the IIC is configured for master transmit but a master receive is
desired, reading the IICxD does not initiate the receive.
Reading the IICxD returns the last byte received while the IIC is configured in master receive or slave
receive modes. The IICxD does not reflect every byte transmitted on the IIC bus, nor can software verify
that a byte has been written to the IICxD correctly by reading it back.
In master transmit mode, the first byte of data written to IICxD following assertion of MST is used for the
address transfer and should comprise of the calling address (in bit 7 to bit 1) concatenated with the required
R/W bit (in position bit 0).
12.3.6 IIC Control Register 2 (IICxC2)
Table 12-8. IICxD Field Descriptions
Field Description
7–0
DATA
Data — In master transmit mode, when data is written to the IICxD, a data transfer is initiated. The most
significant bit is sent first. In master receive mode, reading this register initiates receiving of the next byte of data.
7 6 5 4 3 2 1 0
R
GCAEN ADEXT
0 0 0
AD10 AD9 AD8
W
Reset 0 0 0 0 0 0 0 0
= Unimplemented or Reserved
Figure 12-8. IIC Control Register (IICxC2)
Table 12-9. IICxC2 Field Descriptions
Field Description
7
GCAEN
General Call Address Enable. The GCAEN bit enables or disables general call address.
0 General call address is disabled
1 General call address is enabled
6
ADEXT
Address Extension. The ADEXT bit controls the number of bits used for the slave address.
0 7-bit address scheme
1 10-bit address scheme
2–0
AD[10:8]
Slave Address. The AD[10:8] field contains the upper three bits of the slave address in the 10-bit address
scheme. This field is only valid when the ADEXT bit is set.