S912XET256J2MAL Datasheet, PDF (591/1324 Pages) Freescale Semiconductor, Inc – MC9S12XEP100 Reference Manual Covers MC9S12XE Family

Chapter 15 Inter-Integrated Circuit (IICV3) Block Description
If it were the case that the IBSWAI bit was cleared when the WAI instruction was executed, the IIC internal
clocks and interface would remain alive, continuing the operation which was currently underway. It is also
possible to configure the IIC such that it will wake up the CPU via an interrupt at the conclusion of the
current operation. See the discussion on the IBIF and IBIE bits in the IBSR and IBCR, respectively.
15.3.1.4 IIC Status Register (IBSR)
Module Base + 0x0003
7
6
5
4
3
2
1
0
R TCF
IAAS
IBB
0
SRW
RXAK
IBAL
IBIF
W
Reset
1
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 15-7. IIC Bus Status Register (IBSR)
This status register is read-only with exception of bit 1 (IBIF) and bit 4 (IBAL), which are software
clearable.
Table 15-9. IBSR Field Descriptions
Field
Description
7
Data Transferring Bit — While one byte of data is being transferred, this bit is cleared. It is set by the falling
TCF edge of the 9th clock of a byte transfer. Note that this bit is only valid during or immediately following a transfer
to the IIC module or from the IIC module.
0 Transfer in progress
1 Transfer complete
6
IAAS
Addressed as a Slave Bit — When its own specific address (I-bus address register) is matched with the calling
address or it receives the general call address with GCEN== 1,this bit is set.The CPU is interrupted provided the
IBIE is set.Then the CPU needs to check the SRW bit and set its Tx/Rx mode accordingly.Writing to the I-bus
control register clears this bit.
0 Not addressed
1 Addressed as a slave
5
Bus Busy Bit
IBB
0 This bit indicates the status of the bus. When a START signal is detected, the IBB is set. If a STOP signal is
detected, IBB is cleared and the bus enters idle state.
1 Bus is busy
4
IBAL
Arbitration Lost — The arbitration lost bit (IBAL) is set by hardware when the arbitration procedure is lost.
Arbitration is lost in the following circumstances:
1. SDA sampled low when the master drives a high during an address or data transmit cycle.
2. SDA sampled low when the master drives a high during the acknowledge bit of a data receive cycle.
3. A start cycle is attempted when the bus is busy.
4. A repeated start cycle is requested in slave mode.
5. A stop condition is detected when the master did not request it.
This bit must be cleared by software, by writing a one to it. A write of 0 has no effect on this bit.
3
Reserved — Bit 3 of IBSR is reserved for future use. A read operation on this bit will return 0.
RESERVED
MC9S12XE-Family Reference Manual Rev. 1.25
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