The SZG-TST-TXR is a SYZYGY Transceiver peripheral intended to be used by SYZYGY carrier developers to test continuity during development or production of their carrier. It can be used during automated testing to validate connector I/O.




SYZYGY Information

Compatibility Table

Compatibility ParameterSpecification
Port typeSYZYGY Transceiver
5V supply requiredYes
Nominal 5V supply current< 10mA
Nominal 3.3V supply current< 10mA
VIO supply voltage1.8V
Nominal VIO supply current< 100mA
Total number of I/OUp to 18

DNA Data

This data is stored in the SYZYGY DNA microcontroller on the SZG-PMOD peripheral.

DNA ParameterData
Max 5V Load10 mA
Max 3.3V Load10 mA
Max VIO Load10 mA
VIO Min1.8V
VIO Max1.8V


SYZYGY (J1)ConnectionNote
5 (RX0p)6 (TX0p)Connected through a 0.01 μF AC-coupling capacitor
7 (RX0n)8 (TX0n)Connected through a 0.01 μF AC-coupling capacitor
9 (RX1p)10 (TX1p)Connected through a 0.01 μF AC-coupling capacitor
11 (RX1n)12 (TX1n)Connected through a 0.01 μF AC-coupling capacitor
13 (REFCLKp)REFCLKp125 MHz reference oscillator
15 (REFCLKn)REFCLKn125 MHz reference oscillator
17 (S2)Atmel PB0 (U1 pin 11) 
19 (S4)Atmel PB1 (U1 pin 12) 
21 (S6)Atmel PB2 (U1 pin 14) 
23 (S8)Atmel PA7 (U1 pin 15) 
14 (S0)16 (S1) 
18 (S3)20 (S5) 
22 (S7)24 (S9) 
25 (S10)27 (S12) 
26 (S11)28 (S13) 
29 (S14)31 (S16) 
30 (S15)32 (S17) 
33 (P2C_CLKp)35 (P2C_CLKn) 
34 (C2P_CLKp)36 (C2P_CLKn) 


The SZG-TST-STD is designed to assist carrier developers perform continuity and power supply tests during development and production testing. To accomplish this, the test peripheral connects a communication path from the FPGA to the Atmel MCU for power supply tests. The remaining pins on the connector are shorted together in the manner described below to allow for continuity testing.

Test Firmware

The Atmel MCU on the test peripherals contains a modified version of the normal DNA firmware. The test firmware removes the power supply sequencing options present in the standard firmware.The test firmware also uses the AVR to measure each of the power supply rails, reporting their status back to the FPGA.

Each supply rail is measured with the internal AVR ADC and checked against a pair of threshold values corresponding to the SYZYGY specified tolerance of that power supply rail. If the supply rail is within its required tolerance the AVR sets a "good" status bit for that rail. The VIO rail is assumed to be at 1.8V by the AVR firmware and the DNA for the test peripheral. A 1.8V VIO is used to maximize compatibility with current FPGA I/O supply requirements.

Supply status is communicated back to the FPGA through SYZYGY pins 5, 7, 9, and 11. The AVR continuously reads AVR pin PA7 (SYZYGY Pin 11 (S6)), then outputs the power supply state on the PB[2:0] pins according to the table below.

  +5V Supply+3.3V SupplyVIO Supply
PA7 = 1GoodPB0 = 1PB2 = 1PB1 = 1
BadPB0 = 0PB2 = 0PB1 = 0
PA7 = 0GoodPB0 = 0PB2 = 0PB1 = 0
BadPB0 = 1PB2 = 1PB1 = 1

By toggling the PA7 pin with the FPGA it is possible to test continuity on the MCU pins while also checking the status of each power supply.