## Headstage Tester (HST)

> Only NP 1.0 headstages can be tested in this way, but 1.0 headstages are used with {NP 1.0, NHP, UHD} probes.

### Overview

A headstage can be checked by plugging an imec HST dongle component into that headstage (HS) exactly as you would plug in a probe, and then running the tests in the HST Diagnostics dialog.

Test | Functional Area
--- | ---
Communication | PCLK signal and I2C bus
Supply Voltages | Power connections
Control Signals | NRST control signals
Master Clock | 93.6 MHz master clock
PSB Data Bus | Data bus connectivity
Signal Generator | BIST signal path

    Terminology:
        HW     = hardware
        SW     = software
        PC     = computer
        BIST   = built-in self test
        I2C    = inter-IC bus
        BS     = base station card
        BSC    = base station connect card
        HS     = headstage
        NRST   = State reset signal
        PCLK   = PSB clock
        PSB    = parallel serial bus
        PRBS   = pseudo random binary signal
        SerDes = serializer/deserializer

### Communication

The PCLK test checks the serializer and the connection between the tester and headstage. A failure here is similar to getting a NO_LOCK with a probe.

The I2C bus is the command/control pathway between HS and probe/tester. If this is not working no other tests can run.

### Supply Voltages

This checks the presence of four HS power supply voltages:

- 1.8V analog
- 1.8V digital
- 1.2V analog
- 1.2V digital

### Control Signals

The HST module can check the functionality of the NRST and the REC_NRESET signals between the ZIF connector and serializer on the HS.

### Master Clock

The HST module can verify whether the MCLK clock signal generated on the HS is present.

### PSB Data Bus

The HST module can check the connectivity of the PSB_DATA<0:6> and PSB_SYNC signal on between the ZIF connector and the serializer on the HS. The function first checks PSB_SYNC and continues with PSB_DATA<0> to PSB_DATA<6> consecutively. The function returns at the first failing signal, without checking the remaining signals.

Note: an electrical short-circuit on the input pins of the serializer cannot be detected with the current version of the HST module.

### Signal Generator

The HST module can test the functionality of the test signal generator which is located on the HS and which is primarily used for the BIST pixel signal path test.

The test involves two signals: the output signal coming from the HS: CAL_SIGNAL and the input signal going to the HS which is used to enable or disable the test signal generator, and which is normally coming from the probe: OSC_PDOWN.

fin