PCA9541A All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 5 — 24 April 2014 26 of 45
NXP Semiconductors
PCA9541A
2-to-1 I
2
C-bus master selector with interrupt logic and reset
9.3 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 PCA9541A 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.
9.4 Gatekeeper multiplexer
The PCA9541A/03 can act as a gatekeeper multiplexer in applications where there are
multiple I
2
C-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
I
2
C-bus. Up to 16 hot swappable cards/devices can be multiplexed to the same bus
master by using one PCA9541A/03 per card/device. Since each PCA9541A/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 PCA9541A/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 I
2
C-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 fewer pairs of SDA/SCL traces on the printed-circuit board if the PCA9541A/03 is
used.
Fig 20. Masters with shared resources application
002aae664
PCA9541A
SLAVE A0
SLAVE A1 SLAVE A2
MASTER A
PCA9541A
SLAVE B0
SLAVE B1 SLAVE B2
MASTER B
ASSEMBLY A
ASSEMBLY B
SDA/SCL
SDA/SCL
MAIN
MASTER
