PCA9541_09 Datasheet, PDF (26/41 Pages) NXP Semiconductors – 2-to-1 I2C-bus master selector with interrupt logic and reset

NXP Semiconductors
PCA9541
2-to-1 I²C-bus master selector with interrupt logic and reset
10.3 Masters with shared resources
Some masters may not be multi-master capable or some masters may not work well
together and continually lock up the bus. The PCA9541 can be used to separate the
masters, as shown in Figure 20, but still allow shared access to slave devices, such as
Field Replaceable Unit (FRU) EEPROMs or temperature sensors.
MAIN
MASTER
PCA9541
SLAVE A0
ASSEMBLY A
SLAVE A1
SDA/SCL
SLAVE A2
PCA9541
SLAVE B0
ASSEMBLY B
SLAVE B1
SDA/SCL
SLAVE B2
Fig 20. Masters with shared resources application
MASTER A
MASTER B
002aab614
10.4 Gatekeeper multiplexer
The PCA9541/03 can act as a gatekeeper multiplexer in applications where there are
multiple I²C-bus devices with the same fixed address (for example, EEPROMs with
address of ‘Z’ as shown in Figure 21) connected in a multipoint arrangement to the same
I²C-bus. Up to 16 hot swappable cards/devices can be multiplexed to the same bus
master by using one PCA9541/03 per card/device. Since each PCA9541/03 has its own
unique address (for example, ‘A’, ‘B’, ‘C’, and so on), the EEPROMs can be connected to
the master, one at a time, by connecting one PCA9541/03 (Master 0 position) while
keeping the rest of the cards/devices isolated (off position).
The alternative, shown with dashed lines, is to use a PCA9548 1-to-8 channel switch on
the master card and run 8 I²C-bus devices, one to each EEPROM card, to multiplex the
master to each card. The number of card pins used is the same in either case, but there
are 7 less pairs of SDA/SCL traces on the printed-circuit board if the PCA9541/03 is used.
PCA9541_7
Product data sheet
Rev. 07 — 2 July 2009
© NXP B.V. 2009. All rights reserved.
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