-- SimonBrown - 2012-02-23

This page contains information about the Data Multiplexer for the Pixel Modules.

The Data Multiplexer is intended to be a chip mounted primarily on the ATLAS pixel modules. The main function of the device is to multiplex the data from four FE-I4Bs within a module, so one pair of wires can send data from a module to the ROD. Other potential functions include Manchester decoding of FE-I4 configuration data, clock extraction from Manchester-encoded configuration data (saves a pair of wires) and distribution of clock and/or configuration data to the FE-I4s (providing buffering, data integrity and some degree of Fault-tolerance). It may also be possible to multiplex the output data from the module with the incoming configuration data and clock, to reduce the number of pairs to one (originally 3 - clock, configuration and multiplexed data).

Implementation

Multiplexing may be implemented as nibble- or byte-wise, bit-wise (probably the favourite) or frame-by-frame (may have lockout problems). Other functions are either standard or trivial, meaning that there should not be much design effort required to implement Manchester encoding or serial data buffering, for example. However, it is always a little risky to presume that a design task is relatively easy!

Internal organisation

The device must perform its functions reliably under radiation stress – Fault-tolerant and radhard.

Questions

- Would it be desirable to have temperature measurement (maybe with an on-chip diode and ADC), as with FE-I4s?
- What should be the level of reliability and radhardness, compared to FE-I4s? The whole pixel module depends on the multiplexer, and a higher reliability than the FE-I4 should be achievable since the multiplexer has a lot less logic on it than an FE-I4.