Freescale Semiconductor MCF5480 - Manual (Page 872)

MCF548x Reference Manual, Rev. 3
28-18 Freescale Semiconductor
/* Receive data from master device and store in rx-buffer */
for(i=0; i<rx_byte_count; i++)
{
/* Wait for transfer to complete */
while (!(MCF_I2C_I2SR & MCF_I2C_I2SR_IIF) );
/* Clear IIF bit */
MCF_I2C_I2SR &= 0xFD;
/* Store received data and release SDA */
rx_buffer[i] = MCF_I2C_I2DR;
}
28.5.6 Arbitration Lost
If several masters try to engage the bus simultaneously, only one master wins and the others lose
arbitration. The devices which lost arbitration are immediately switched to slave receive mode by the
hardware. Their master that has lost arbitration immediately releases the bus, but SCL is still generated
until the end of the byte during which arbitration was lost. An interrupt occurs at the falling edge of the
ninth clock of this transfer with IAL = 1 and MSTA = 0.
If the MCF548x attempts to start transmission while the bus is being engaged by another master, the
hardware will inhibit the transmission, switch the MSTA bit from 1 to 0 without generating a STOP
condition, generate an interrupt to the CPU, and set the IAL bit to indicate that the attempt to engage the
bus has failed. When considering these cases, the slave service routine should test the IAL bit first, and the
software should clear the IAL bit if it is set.
28.5.7 Flow Control
Figure 28-14 displays the flow of a typical I
2
C interrupt process.