Knowledge Base - How does the slow-control work ?
The slow control is a shift register composed of n flip flops (Refer to the datasheet of the corresponding chip to know how much they are). Data are memorized in flip flops on leading edge of the clock. The data are shifted at each clock cycle as seen on figure 1. Between "srout" and the output of the last slow control register’s flip flop, there is another flip flop clocked on !clk so an additional falling edge is needed to send the data out on srout.
Figure 1: Slow control chronogram and schematic
The slow control is used to tune parameters such as preamplifier gains, shaping times for the slow shapers, enable/disable blocks, etc. Refer to the datasheet of the corresponding ROC chip for more informations on slow control parameters.
The bitstream for the slow control parameters have to be sent through the "srin" pin and the pre-existing slow control parameters (already inside the chip) are pushed bit by bit through the "srout" pin. At the start-up of the chip the default slow control parameters are already inside the chip and can be read-out using this. By sending the slow control parameters two times in a row, the user can read-out the parameters sent the first time and verify the integrity of the bistream.
On some chips, there is also a probe register. This register is also sent via the "srin" pin and a "select" pin allows to chose if the bistream is sent in the slow control register or the probe register.
Created : 2015-02-18 14:16:03, Last Modified : 2015-02-18 15:35:00