4 slave transmitter mode, Nxp semiconductors – NXP Semiconductors LPC24XX UM10237 User Manual
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UM10237_4
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User manual
Rev. 04 — 26 August 2009
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NXP Semiconductors
UM10237
Chapter 22: LPC24XX I
2
C interfaces I
2
C0/1/2
9.4 Slave Transmitter mode
In the slave transmitter mode, a number of data bytes are transmitted to a master receiver
(see
). Data transfer is initialized as in the slave receiver mode. When
I2ADR and I2CON have been initialized, the I
2
C block waits until it is addressed by its own
slave address followed by the data direction bit which must be “1” (R) for the I
2
C block to
operate in the slave transmitter mode. After its own slave address and the R bit have been
received, the serial interrupt flag (SI) is set and a valid status code can be read from
I2STAT. This status code is used to vector to a state service routine, and the appropriate
action to be taken for each of these status codes is detailed in
. The slave
transmitter mode may also be entered if arbitration is lost while the I
2
C block is in the
master mode (see state 0xB0).
If the AA bit is reset during a transfer, the I
2
C block will transmit the last byte of the transfer
and enter state 0xC0 or 0xC8. The I
2
C block is switched to the not addressed slave mode
and will ignore the master receiver if it continues the transfer. Thus the master receiver
receives all 1s as serial data. While AA is reset, the I
2
C block does not respond to its own
slave address or a general call address. However, the I
2
C bus is still monitored, and
address recognition may be resumed at any time by setting AA. This means that the AA
bit may be used to temporarily isolate the I
2
C block from the I
2
C bus.
Fig 123. Format and States in the Slave Transmitter mode
DATA
A
A
R
SLA
S
P OR S
A
A
B0H
A8H
C0H
C8H
last data byte
transmitted. Switched
to Not Addressed
Slave (AA bit in
I2CON = “0”)
arbitration lost as
Master and
addressed as Slave
reception of the own
Slave address and
one or more Data
bytes all are
acknowledged
from Master to Slave
from Slave to Master
any number of data bytes and their associated
Acknowledge bits
n
this number (contained in I2STA) corresponds to a defined state of
the I
2
C bus
A
DATA
B8H
ALL ONES
A
DATA
P OR S