TPCE636 User Manual Issue 1.0.2
Page 49 of 104
7.6.2 Si514 Free Programming Clock source
A second clock source is the free programmable Si514 XO from Silicon Laboratories.
The Si514 is programmable via I2C interface. An internal PLL allows output frequency of 100 kHz up to 250
MHz with programming resolution of 0.026 parts per billion.
The Si514 on TPCE636 is factory configured to 156 MHz default frequency.
The Si514 is connected via I2C interface to User FPGA (Kintex-7). As usual for the I2C interface, the two
pins must be realized as open drain buffer. The same I2C interface is used for the calibration data prom.
Si514 I2C Bus
Signal
Bank
V
CCO
Pin
Description / Kintex-7
USER_SCL
14
3.3V
F25
Serial clock
USER_SDA
14
3.3V
G26
Serial data
Table 7-7 : FPGA I2C SI514 Connections
Configuration and operation of the Si514 is controlled by reading and writing to the Si514 internal RAM
space using the I2C interface. The device operates in slave mode with 7-bit addressing and can operate in
Standard-Mode (100kbps) or Fast-Mode (400kbps).
The I2C 7-bit slave address of the Si514 is 0x55h.
To use the serial I2C interface between the USER FPGA (Kintex-7) and the Si514 please also see the
Silicon Labs Si514 data sheet which describes the register map and serial communication process.
