PCA9541 データシートの表示（PDF） - NXP Semiconductors.
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PCA9541 Datasheet PDF : 41 Pages
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NXP Semiconductors
PCA9541
2-to-1 I2C-bus master selector with interrupt logic and reset
• During a write operation, the PCA9541 will acknowledge bytes sent to the IE and
CONTROL registers, but will not acknowledge a byte sent to the Interrupt Status
Register since it is a read-only register. The 2 LSBs of the Command Code do not roll
over to 00b but stay at 10b.
Only the 2 least significant bits are affected by the AI flag.
Unused bits must be programmed with zeros. Any command code (write operation)
different from ‘000AI 0000’, ‘000AI 0001’, and ‘000AI 0010’ will not be acknowledged. At
power-up, this register defaults to all zeros.
Table 4. Command Code register
B1
B0
Register name
Type
0
0
IE
R/W
0
1
CONTROL
R/W
1
0
ISTAT
R only
1
1
not allowed
Register function
interrupt enable
control switch
interrupt status
Each system master controls its own set of registers, however they can also read specific
bits from the other system master.
IE
REG#00
CONTROL REG#01
ISTAT
REG#10
MASTER 0
SCL_MST0
SDA_MST0
PCA9541
IE 0
IE 1
CONTROL 0
CONTROL 1
ISTAT 0
ISTAT 1
002aab392
Fig 7. Internal register map
REG#00
IE
REG#01 CONTROL
REG#10
ISTAT
MASTER 1
SCL_MST1
SDA_MST1
8.3 Interrupt Enable and Control registers description
When a master seeks control of the bus by connecting its I2C-bus channel to the
PCA9541 downstream channel, it has to write to the CONTROL register (Reg#01).
Bits MYBUS and BUSON allow the master to take control of the bus.
The MYBUS and the NMYBUS bits determine which master has control of the bus.
Table 9 explains which master gets control of the bus and how. There is no arbitration. Any
master can take control of the bus when it wants regardless of whether the other master is
using it or not.
The BUSON and the NBUSON bits determine whether the upstream bus is connected or
disconnected to/from the downstream bus. Table 10 explains when the upstream bus is
connected or disconnected.
Internally, the state machine does the following:
• If the combination of the BUSON and the NBUSON bits causes the upstream to be
disconnected from the downstream bus, then that is done. So in this case, the values
of the MYBUS and the NMYBUS do not matter.
PCA9541_7
Product data sheet
Rev. 07 — 2 July 2009
© NXP B.V. 2009. All rights reserved.
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