4 I2C Communication
4.1 Overview
The I2C bus on the Mercury ZX1 SoC module is connected to the SoC device, EEPROM and RTC, and is
available on the module connector. This allows external devices to read the module type and to connect
more devices to the I2C bus.
Please note that the RTC must be configured correctly to use I2C interrupts - for details, refer to Section 2.23.
The I2C clock frequency should not exceed 400 kHz.
Warning!
Maximum I2C speed may be limited by the routing path and additional loads on the base board.
Warning!
If the I2C traces on the base board are very long, 100 Ω series resistors should be added between
module and I2C device on the base board.
4.2 Signal Description
Table 40 describes the signals of the I2C interface. All signals have on-board pull-up resistors to VCC_3V3.
All signals must be connected to open collector outputs and must not be driven high from any source.
I2C_INT# is an input to the SoC and must not be driven from the SoC device.
Level shifters are used between the I2C bus and the PS/PL pins, to allow I/O voltages lower than 3.3 V. Please
make sure that all pins are configured correctly and no pull-down resistors are enabled.
Signal Name PS Pin PL Pin Connector Pin Resistor
I2C_SDA MIO53
10
Y13 A-113 2.2 kΩ pull-up
I2C_SCL MIO52
10
W13 A-111 2.2 kΩ pull-up
I2C_INT# - K10 A-115 10 kΩ pull-up
Table 40: I2C Signal Description
4.3 I2C Address Map
Table 41 describes the addresses for several devices connected on I2C bus.
10
MIO52 and MIO53 are used for MDIO by default. Please refer to Section 2.9.8 for details.
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