Version 1.0
Page 19
Table 15
–I2C MUX/SWITCH Channel Usage
The following figure describes the addressing required to access the I2C Switch/MUX. Please see the
appropriate device datasheet for further details regarding transactions to and from this device.
Figure 9
– I2C Switch/MUX Addressing
2.7.1
End-User Carrier Card I2C Interface
The UltraZed-EG SOM provides a master two-wire serial bus (
CC_SDA
,
CC_SCL
, and
CC_INT_N
) to the
end-user carrier card via the JX3 connector so that software can communicate with all I2C devices on the
UltraZed-EG SOM as well as the slave I2C devices on the end-user carrier card using a single two-wire
serial interface.
The end-user carrier card two-wire serial interface is connected to channel 0 of the 2-channel switch/mux
device. End-user carrier cards can drive the
INT0_N
of the channel 0 via
CC_INT_N
, if they so desire. The
CC_INT_N
(an
active low
signal) is not specific to the I2C interface and can be used as a general-purpose
interrupt from end-user carrier cards to the UltraZed-EG SOM. If not used, the
CC_INT_N
signal is to be
pulled up to 1.8V, 2.5V, or 3.3V on the Carrier Card. Since channel 0 I2C bus is dedicated to the end-user
carrier card, two-wire serial devices with any address can reside on this bus without conflicting with the I2C
devices on the UltraZed-EG SOM.
Table 16
– Carrier Card I2C Net Mapping
Switch/MUX
NAME
Switch/MUX
PIN
FUNCTION
NET NAME JX3 CONNECTOR
INT0_N
4
INTERRUPT0
CC_INT_N
JX3.68
SD0
5
SERIAL DATA0
CC_SDA
JX3.41
SC0
6
SERIAL CLOCK0
CC_SCL
JX3.44
Switch/MUX Channel
Usage
Notes
Master Channel
(SDA/SCL/INT)
This channel is connected to the PS I2C port, MIO [24:25] and
operated at 1.8V. The master
INT_N
output is connected to the P4
port of the I2C 8-bit I/O expander.
Pulled-up to
1.8V on the
SOM
Slave Channel 0
(SD0/SC0/INT0)
This channel is connected to the JX3 connector (
CC_SDA
,
CC_SCL
, and
CC_INT_N
signals) to allow slave I2C devices on the
Carrier Card to be virtually placed on the same PS I2C bus (MIO
[24:25]) as the I2C devices on the UltraZed-EG SOM so that
software can use a single PS I2C core to communicate with all I2C
devices in the system.
Pulled-up to
1.8V, 2.5V, or
3.3V on the
Carrier Card
Slave Channel 1
(SD1/SC1/INT1)
This channel is connected to the PMBus (
PMBUS_SDA
and
PMBUS_SCL
signals) of the UltraZed-EG SOM PMBus voltage
regulators and used to control all PMBus voltage regulators on the
UltraZed-EG SOM as well as the Carrier Card (the PMBus is
connected to the Carrier Card via JX2 connector).
This feature will allow the PS to control/monitor the PMBus voltage
regulators on the UltraZed-EG SOM as well as the Carrier Card for
the purpose of power management and/or measurements.
Pulled-up to
3.3V on the
SOM
The unused
slave channel
1
INT1_N
input
must be pulled
up to the VCC
(2.5V) rail.