Some Special Cases; Simultaneous Repeated Start Conditions From Two Masters; Data Transfer After Loss Of Arbitration; Forced Access To The I C-Bus - Philips LPC2101 User Manual

Philips Semiconductors
Volume 1
Table 137: Miscellaneous States
Status Status of the I
Code and hardware
(I2CSTAT)
0xF8 No relevant state
information available;
SI = 0.
0x00 Bus error during MST
or selected slave
modes, due to an
illegal START or
STOP condition. State
0x00 can also occur
when interference
2
causes the I C block
to enter an undefined
state.

11.8.8 Some special cases

The I
a serial transfer:

11.8.9 Simultaneous repeated START conditions from two masters

A repeated START condition may be generated in the master transmitter or master
receiver modes. A special case occurs if another master simultaneously generates a
repeated START condition (see
master since they were both transmitting the same data.
If the I
a repeated START condition itself, it will release the bus, and no interrupt request is
generated. If another master frees the bus by generating a STOP condition, the I
will transmit a normal START condition (state 0x08), and a retry of the total serial data
transfer can commence.

11.8.10 Data transfer after loss of arbitration

Arbitration may be lost in the master transmitter and master receiver modes (see
Figure
0x78, and 0xB0 (see
If the STA flag in I2CON is set by the routines which service these states, then, if the bus
is free again, a START condition (state 0x08) is transmitted without intervention by the
CPU, and a retry of the total serial transfer can commence.
11.8.11 Forced access to the I
In some applications, it may be possible for an uncontrolled source to cause a bus
hang-up. In such situations, the problem may be caused by interference, temporary
interruption of the bus or a temporary short-circuit between SDA and SCL.

User manual

2
C-bus Application software response
To/From I2DAT
No I2DAT action
No I2DAT action
2
C hardware has facilities to handle the following special cases that may occur during
2
C hardware detects a repeated START condition on the I
30). Loss of arbitration is indicated by the following states in I2STAT; 0x38, 0x68,
Figure 32
Rev. 01 — 12 January 2006
Next action taken by I
To I2CON
STA STO SI AA
No I2CON action Wait or proceed current transfer.
0 1 0 X Only the internal hardware is affected in
the MST or addressed SLV modes. In all
cases, the bus is released and the I
block is switched to the not addressed
SLV mode. STO is reset.
Figure 36). Until this occurs, arbitration is not lost by either
and Figure 33).
2
C-bus
UM10161
2
Chapter 11: I C interfaces
2
C hardware
2
C-bus before generating
2
C block
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
2
C
146