ML51/ML54/ML56
Sep. 01, 2020
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Rev 2.00
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TECHNI
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ML51/M
L54
/M
L56
Series
Tec
hnical Reference
Manual
Bit
Name
Description
[3]
SI
I2Cn Interrupt Flag
SI flag is set by hardware when one of 26 possible I
2
C status (besides F8H status) is
entered. After SI is set, the software should read I2CnSTAT register to determine which
step has been passed and take actions for next step.
SI is cleared by software. Before the SI is cleared, the low period of SCL line is stretched.
The transaction is suspended. It is useful for the slave device to deal with previous data
bytes until ready for receiving the next byte.
The serial transaction is suspended until SI is cleared by software. After SI is cleared, I
2
C
bus will continue to generate START or repeated START condition, STOP condition, 8-bit
data, or so on depending on the software configuration of controlling byte or bits. Therefore,
user should take care of it by preparing suitable setting of registers before SI is software
cleared.
[2]
AA
Acknowledge Assert Flag
If the AA flag is set, an ACK (low level on SDA) will be returned during the acknowledge
clock pulse of the SCL line while the I
2
C device is a receiver or an own-address-matching
slave.
If the AA flag is cleared, a NACK (high level on SDA) will be returned during the
acknowledge clock pulse of the SCL line while the I
2
C device is a receiver or an own-
address-matching slave. A device with its own AA flag cleared will ignore its own salve
address and the General Call. Consequently, SI will note be asserted and no interrupt is
requested.
Note that if an addressed slave does not return an ACK under slave receiver mode or not
receive an ACK under slave transmitter mode, the slave device will become a not
addressed slave. It cannot receive any data until its AA flag is set and a master addresses
it again.
There is a special case of I2CnSTAT value C8H occurs under slave transmitter mode.
Before the slave device transmit the last data byte to the master, AA flag can be cleared as
0. Then after the last data byte transmitted, the slave device will actively switch to not
addressed slave mode of disconnecting with the master. The further reading by the master
will be all FFH.
[1:0]
-
Reserved
SCL
SDA
SDA to SCL Hold time extend
Figure 6.12 Hold Time extend enable