UM10850
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© NXP B.V. 2016. All rights reserved.
User manual
Rev. 2.4 — 13 September 2016
328 of 464
NXP Semiconductors
UM10850
Chapter 23: LPC5410x I2C-bus interfaces (I2C0/1/2)
23.6.15 Monitor data register
The read-only MONRXDAT register provides information about events on the I
2
C bus,
primarily to facilitate debugging of the I
2
C during application development. All data
addresses and data passing on the bus and whether these were acknowledged, as well
as Start and Stop events, are reported.
The Monitor function must be enabled by the MONEN bit in the CFG register. Monitor
mode can be configured to stretch the I
2
C clock if data is not read from the MONRXDAT
register in time to prevent it, via the MONCLKSTR bit in the CFG register
.
This can help
ensure that nothing is missed but can cause the monitor function to be somewhat intrusive
(by potentially adding clock delays, depending on software or DMA response time). In
order to improve the chance of collecting all Monitor information if clock stretching is not
enabled, Monitor data is buffered such that it is available until the end of the next piece of
information from the I
2
C bus.
Details of clock stretching are different in HS mode, see
.
Table 371. Address map MONRXDAT register
Peripheral
Base address
Offset
Increment
Dimension
I2C0
0x4009 4000
0x080
-
1
I2C1
0x4009 8000
0x080
-
1
I2C2
0x4009 C000
0x080
-
1
Table 372. Monitor data register (MONRXDAT, address offset 0x080) bit description
Bit
Symbol
Value Description
Reset
value
7:0
MONRXDAT
Monitor function Receiver Data. This reflects every data byte that passes on the
I
2
C pins.
0
8
MONSTART
Monitor Received Start.
0
0
No start detected. The monitor function has not detected a Start event on the I
2
C
bus.
1
Start detected. The monitor function has detected a Start event on the I
2
C bus.
9
MONRESTART
Monitor Received Repeated Start.
0
0
No repeated start detected. The monitor function has not detected a Repeated
Start event on the I
2
C bus.
1
Repeated start detected. The monitor function has detected a Repeated Start
event on the I
2
C bus.
10
MONNACK
Monitor Received NACK.
0
0
Acknowledged. The data currently being provided by the monitor function was
acknowledged by at least one master or slave receiver.
1
Not acknowledged. The data currently being provided by the monitor function was
not acknowledged by any receiver.
31:11
-
Reserved. Read value is undefined, only zero should be written.
NA