Nxp Semiconductors UM10237 ユーザーズマニュアル

UM10237_2

© NXP B.V. 2008. All rights reserved.

There are two I2STAT codes that do not correspond to a defined I

2

C hardware state (see 

). These are discussed below.

This status code indicates that no relevant information is available because the serial 
interrupt flag, SI, is not yet set. This occurs between other states and when the I

2

C block 

is not involved in a serial transfer.

This status code indicates that a bus error has occurred during an I

2

C serial transfer. A 

bus error is caused when a START or STOP condition occurs at an illegal position in the 
format frame. Examples of such illegal positions are during the serial transfer of an 
address byte, a data byte, or an acknowledge bit. A bus error may also be caused when 
external interference disturbs the internal I

2

C block signals. When a bus error occurs, SI is 

set. To recover from a bus error, the STO flag must be set and SI must be cleared. This 
causes the I

2

C block to enter the “not addressed” slave mode (a defined state) and to 

clear the STO flag (no other bits in I2CON are affected). The SDA and SCL lines are 
released (a STOP condition is not transmitted).