PCA9541_7 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2015. All rights reserved.
Product data sheet Rev. 7.1 — 24 June 2015 26 of 42
NXP Semiconductors
PCA9541
2-to-1 I
2
C-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.
10.4 Gatekeeper multiplexer
The PCA9541/03 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 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 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 less pairs of SDA/SCL traces on the printed-circuit board if the PCA9541/03 is used.
Fig 20. Masters with shared resources application
002aab614
PCA9541
SLAVE A0
SLAVE A1 SLAVE A2
MASTER A
PCA9541
SLAVE B0
SLAVE B1 SLAVE B2
MASTER B
ASSEMBLY A
ASSEMBLY B
SDA/SCL
SDA/SCL
MAIN
MASTER
