SiPM digital control board supporting components

Overview

While the FPGA, Ethernet controller, DAC, ADC and Temperature sensor are considered the main components of the SiPM digital control board, there are also many other supporting components that will be on the board. This page discusses many of the other minor components on the SiPM digital control board.

FPGA Supporting Components

XCF01S EEPROM

Connection diagram for XCF01S and Spartan-3A FPGA taken from
XCF01S specifications sheet.

The Xilinx XCF01S EEPROM is responsible for configuring the FPGA when the system is turned on or reset. We selected the XCF01S because it is recommended by Xilinx as the best solution for programming the Spartan-3A FPGA used on the control board. The XCF01S is ideal because it has sufficient memory to hold the entire FPGA program, and also minimizes the number of FPGA-to-EEPROM leads necessary for programming the FPGA. For more information on the mode of programming the FPGA, see FPGA programming modes.

TODO: Insert information about logic levels.

Post-Configuration EEPROM Isolating Logic

It may be necessary to introduce OR gates and NOR gates (with the FPGA's DONE pin) to keep EEPROM pins at the necessary logic values after programming is complete, if the configuration pins on the FPGA will be reused as user I/O pins following configuration. Research must be done into whether this logic is necessary. The specifications sheet for the XCF01S says that when CE is held high, the D0 pin goes into a high impedance state. What is not clear is if changing logic values on the others pins will have an adverse effect when CE is high.

FPGA/EEPROM Pull-up Resistors

As shown in the connection diagram, 4.7kΩ pull-up resistors are necessary to pull up the DONE, INIT_B and PROG_B pins to VCCO.