Digital control board documentation
This documentation covers the most important things to know while testing the digital control board, including component pinouts, nets, and other information.
Power Requirements
Required Voltages
All components on the digital board except the DAC can be tested using only a +5V source. The DAC requires +5V, -5V, and a high voltage corresponding to 10V higher than the maximum desired DAC output voltage (see Setting the Output Range). Digital and analog grounds must be connected as well before any testing takes place.
Power Pins
Power shall be connected to the board as follows:
| Voltage | Eurocard Pin |
| DGND | A6 |
| AGND | A5 |
| +5V | A4 |
| -5V | A3 |
| High voltage (DAC max out +10) |
A2 |
Power Supply Sequencing
The control board is designed such that voltages may be supplied in any order so long as AGND and DGND are connected properly. However, for initial testing, the preferred order for powering up the board is as follows:
- Ensure AGND/DGND are connected/grounded
- +5V
- -5V
- High voltage
FPGA
The control board uses a Xilinx XC3S50A VQ100 FPGA. It has a 100 pin footprint and is located in the center of the control board.
Power Details
The FPGA is powered by the 3.3V power plane, which is regulated by VR1. The FPGA also obtains 1.2V for its internal logic from a 1.2V power island, regulated by VR3.
Logic Standard
The Xilinx XC3S50A supports several different digital logic standards. The control board is hard wired such that the FPGA will use a 3.3V CMOS logic standard.
Pinout Table
| Pin # | Net Name | Signal Name | Description |
| P1 | FPGA/TMS | JTAG | |
| P2 | FPGA/TDI | JTAG | |
| P3 | AD7928/CS | SPI chip select for ADC | |
| P4 | SPI | Erroneously wired SPI bus trace Connects to SDO on temp. sensor and DIN on ADC | |
| P5 | CLK_5MHZ | 5 MHz clock output for SPI bus (ADC and temp. sensor) | |
| P6 | No connection | ||
| P7 | No connection | ||
| P8 | DGND | ||
| P9 | No connection | ||
| P10 | No connection | ||
| P11 | +3.3V | ||
| P12 | No connection | ||
| P13 | No connection | ||
| P14 | DGND | ||
| P15 | No connection | ||
| P16 | No connection | ||
| P17 | +1.2V | ||
| P18 | DGND | ||
| P19 | No connection | ||
| P20 | No connection | ||
| P21 | No connection | ||
| P22 | +3.3V | ||
| P23 | DGND | ||
| P24 | DGND | ||
| P25 | DGND | ||
| P26 | +3.3V | ||
| P27 | FPGA/CLK_IN | 20 MHz clock input from crystal oscillator | |
| P28 | No connection | ||
| P29 | No connection | ||
| P30 | No connection | ||
| P31 | No connection | ||
| P32 | No connection | ||
| P33 | No connection | ||
| P34 | No connection | ||
| P35 | CP2201/INT | Ethernet controller interrupt | |
| P36 | MASTER_RESET | Connects to RESET jumper in upper left of board (active-low, externally pulled up) | |
| P37 | No connection | ||
| P38 | +1.2V | ||
| P39 | No connection | ||
| P40 | CP2201/CS | Chip select for ethernet controller | |
| P41 | CP2201/WR | Write enable for ethernet controller | |
| P42 | DGND | ||
| P43 | CP2201/RD | Read enable for ethernet controller | |
| P44 | CP2201/ALE | Address line enable for ethernet controller | |
| P45 | +3.3V | ||
| P46 | CP2201/RESET | Reset pin for ethernet controller | |
| P47 | DGND | ||
| P48 | FPGA/INIT_B | Used during FPGA configuration - see Xilinx documentation | |
| P49 | CP2201/AD0 | Ethernet controller address/data bus, bit 0 | |
| P50 | CP2201/AD1 | Ethernet controller address/data bus, bit 1 | |
| P51 | FPGA/DIN | Serial data input from EEPROM for configuration | |
| P52 | CP2201/AD2 | Ethernet controller address/data bus, bit 2 | |
| P53 | FPGA/CCLK | Configuration clock (signal generated by FPGA at power on to clock the configuration process) See Xilinx documentation | |
| P54 | FPGA/DONE | Gives configuration status - see Xilinx documentation | |
| P55 | +3.3V | ||
| P56 | CP2201/AD3 | Ethernet controller address/data bus, bit 3 | |
| P57 | CP2201/AD4 | Ethernet controller address/data bus, bit 4 | |
| P58 | DGND | ||
| P59 | CP2201/AD5 | Ethernet controller address/data bus, bit 5 | |
| P60 | CP2201/AD6 | Ethernet controller address/date bus, bit 6 | |
| P61 | CP2201/AD7 | Ethernet controller address/date bus, bit 7 | |
| P62 | No connection | ||
| P63 | DGND | ||
| P64 | No connection | ||
| P65 | No connection | ||
| P66 | +1.2V | ||
| P67 | +3.3V | ||
| P68 | +3.3V | ||
| P69 | DGND | ||
| P70 | ID3 | Backplane location identifier jumper, pins 3 & 4 Active-low, FPGA should pull high | |
| P71 | ID2 | Backplane location identifier jumper, pins 5 & 6 Active-low, FPGA should pull high | |
| P72 | ID1 | Backplane location identifier jumper, pins 7 & 8 Active-low, FPGA should pull high | |
| P73 | ID0 | Backplane location identifier jumper, pins 9 & 10 Active-low, FPGA should pull high | |
| P74 | DGND | ||
| P75 | FPGA/TDO | JTAG | |
| P76 | FPGA/TCK | JTAG | |
| P77 | ID4 | Backplane location identifier jumper, pins 1 & 2 Active-low, FPGA should pull high | |
| P78 | No connection | ||
| P79 | +3.3V | ||
| P80 | DGND | ||
| P81 | +1.2V | ||
| P82 | No connection | ||
| P83 | CLK_5MHZ_2 | 5 MHz clock output for DAC | |
| P84 | No connection | ||
| P85 | AD5535/DIN | DAC serial data input (FPGA out -> DAC in) | |
| P86 | No connection | ||
| P87 | DGND | ||
| P89 | No connection | ||
| P90 | No connection | ||
| P91 | DGND | ||
| P92 | +3.3V | ||
| P93 | AD7314/CE | Chip enable for temperature sensor | |
| P94 | No connection | ||
| P95 | DGND | ||
| P96 | +3.3V | ||
| P97 | AD7928/DOUT | Erroneously wired ADC SPI bus connection Connects to DOUT on ADC | |
| P98 | AD5535/RESET | Reset pin for DAC | |
| P99 | DGND | ||
| P100 | FPGA/PROG_B | Used during FPGA configuration - see Xilinx documentation |
EEPROM
To facilitate power-on configuration of the FPGA, the control board includes a Xilinx XCF01S EEPROM. The EEPROM is located to the left of the FPGA, above the JTAG header, and has a 20 pin footprint. The EEPROM is labelled U5.
Power Details
The EEPROM uses +3.3V exclusively, which it receives from the +3.3V power plane, regulated by VR1.
Flashing/Burning/Writing
Whatever you call it, this refers to storing data in the EEPROM so that it can configure the FPGA at power-on. The EEPROM is programmed using a JTAG interface and the Xilinx Platform USB II cable. It is important to note that in digital board's JTAG chain, the EEPROM is the first device in the chain, unlike in the Xilinx documentation where it is shown as the second device. This should not affect the operation of the board, but should be reflected in the Xilinx software when writing the EEPROM via JTAG.
FPGA Configuration
The EEPROM and FPGA are hardwired to use a master serial protocol to transfer the program from the EEPROM to the FPGA. This is the protocol recommended in the Xilinx documentation because it minimizes the number of traces necessary to run between the EEPROM and FPGA. All configuration data is sent over a single trace, FPGA/DIN (pin 1 on EEPROM), controlled by the configuration clock signal (FPGA/CCLK) which is automatically generated by the FPGA at power-on. When configuration is complete, FPGA/DONE (pin 10) is pulled high by the FPGA, and the EEPROM and configuration clock are deactivated.
Pinout Table
| Pin # | Net Name | Description |
| 1 | FPGA/DIN | Serial data line Carries data from the EEPROM to the FPGA |
| 2 | No connection | |
| 3 | FPGA/CCLK | Configuration clock Auto generated by FPGA at power-on, disabled at end of configuration |
| 4 | EEPROM/TDI | This is the EEPROM's TDI This is the entry point for the onboard JTAG chain |
| 5 | FPGA/TMS | JTAG TMS Connects to both FPGA and EEPROM |
| 6 | FPGA/TCK | JTAG TCK Connects to both FPGA and EEPROM |
| 7 | FPGA/PROG_B | Used during configuration See Xilinx documentation |
| 8 | FPGA/INIT_B | Used during configuration - can be used to intiate reconfiguration of FPGA See Xilinx documentation |
| 9 | No connection | |
| 10 | FPGA/DONE | Indicates completion of FPGA configuration High when complete |
| 11 | DGND | |
| 12-16 | No connection | |
| 17 | FPGA/TDI | This is the EEPROM's TDO/FPGA's TDI |
| 18-20 | +3.3V |
JTAG Header
To write the FPGA's program to the EEPROM, the board employs a JTAG based programming system consistent with Xilinx's recommendations. The system is designed to operate with Xilnx's Platform USB II cable and the flying lead adapter.
Header Location and Size
The header consists of 14 pins, 100 mil pitch, just below the EEPROM (U5). The header is labelled P1. The pitch of the pins in the header was erroneously selected to be 100 mil, which is not compatible with Xilinx's JTAG ribbon cable. Therefore, the Xilinx flying lead adapter must be used.
Power Details
The JTAG interface is powered by the +3.3V power plane, not by the computer's USB port. Power is supplied through pin 2 of the JTAG header.
Pinout Table
Note that the header is positioned on the board rotated 180 degrees from the position in which it is shown in the Xilinx documentation. Care must be taken when connecting the flying leads to ensure they are connected to the right pins. Improper wiring will certainly cause undesired operation, and may cause damage as well. Damage is most likely to occur if one of the flying leads is improperly connected to an odd numbered pin, since it will short to the PCB's ground plane.
| Pin # | Net Name | Flying Lead | Description |
| 1, 3, 5, 7, 9, 11, 13 (odd pins) | DGND | Black (connect to any odd numbered pin) | Ground pins for signal integrity Never connect a flying lead other than the black lead to an odd numbered pin Doing so will short to ground and may cause permanent damage if the Platform USB II cable does not have protection against this. |
| 2 | +3.3V | Red/VREF | Power source for all JTAG logic |
| 4 | FPGA/TMS | Green/TMS | JTAG TMS - connects to EEPROM and FPGA |
| 6 | FPGA/TCK | Yellow/TCK | JTAG TCK - connects to EEPROM and FPGA |
| 8 | FPGA/TDO | Purple/TDO | JTAG boundary scan chain endpoint |
| 10 | EEPROM/TDI | White/TDI | JTAG boundary scan chain start point |
| 12 | No connection | Pin is floating | |
| 14 | No connection | Pin is floating |
The gray HALT flying lead is not connected.
JTAG Overview
The JTAG interface is clocked by the TCK signal. TCK is generated by the Platform USB II cable, and connects directly from the JTAG header to both the EEPROM and FPGA.
The TMS signal is directly connected to both the EEPROM and FPGA, and is the data line over which JTAG test results (in this case programming results) are sent. TMS is used by only one component at a time.
The TDI/TDO lines form a chain that connects to each JTAG component in series. On the control board, the first point in the chain is the EEPROM's TDI. Next is the EEPROM's TDO, which is the same as the FPGA's TDI. The FPGA's TDO then returns to the JTAG header and the Platform USB II cable.
DAC
The control board uses the Analog Devices AD5535, 32-channel, 200V max, digital to analog converter. This chip has a modified BC-124 BGA footprint and is located above the Eurocard connector at the bottom of the board. It is labelled U3.
Power Details
The DAC is primarily powered by the +5V power island, regulated by an off-board power supply and extensively decoupled in the area of the DAC. The DAC also requires -5V, and a high voltage as discussed in Power Requirements. Both of these voltages are supplied by an off-board supply and decoupled near the DAC. In addition to these voltage levels, the DAC requires a precise +2.5V reference, created by the shunt-type voltage reference VR4.
Setting the Output Range
The output range of the DAC is set by the 2.5V reference voltage supplied by VR4. The high voltage power supply must supply at a minimum 50 times this voltage, plus 10. Thus, the high voltage power supply should be at least 135V for DAC to operate properly, even though the SiPMs are expected to need only 40V. If it is convenient to use a lower high voltage, VR4 must be replaced to provide lower reference voltage. The high voltage may then be decreased appropriately. To summarize:
- Max output voltage = VREF*50
- Minimum high voltage supply = VREF*50 + 10
- Acceptable range for VREF
- Min: 1V
- Max: 3.75V (AD5535 datasheet specifies 4V max, but this would require AVCC of 5.25V for the DAC, which is not possible in the current board design)
If relevant, R13 is a 100K resistor.
Thermal Diode
The DAC has a built in thermal diode. The diode drop from anode to cathode is typically 0.65V at 25°C. It changes at a rate of -2.20mV/°C. The anode of this diode is connected to the +5V power island, and the cathode is connected to a 270K resistor to ground. The voltage between the cathode and the resistor is connected to VIN1 (pin 15) on the ADC.
Pinout Table
See documentation from Analog Devices.
Channel Mapping
Due to the layout of the balls on the footprint of the DAC, the DAC's internal channel numbers (which must be referenced by the FPGA) have no correlation to the channel numbers on the amplifier board. This table summarizes the mapping between various pins that belong to each channel.
| DAC Channel # | DAC Pin # | Digital Board Eurocard Pin # | Amplifier Board Eurocard Pin # | Amplifier Channel # |
| 0 | B1 | B3 | ||
| 1 | A2 | C4 | ||
| 2 | D1 | B2 | ||
| 3 | C2 | C3 | ||
| 4 | B3 | B4 | ||
| 5 | E2 | C2 | ||
| 6 | F3 | B1 | ||
| 7 | A4 | B5 | ||
| 8 | E4 | C5 | ||
| 9 | B5 | C6 | ||
| 10 | F5 | C1 | ||
| 11 | A6 | C7 | ||
| 12 | E6 | B6 | ||
| 13 | B7 | B7 | ||
| 14 | F7 | C10 | ||
| 15 | E8 | C8 | ||
| 16 | A8 | B8 | ||
| 17 | B9 | C9 | ||
| 18 | F9 | C16 | ||
| 19 | E10 | B11 | ||
| 20 | A10 | B9 | ||
| 21 | B11 | B10 | ||
| 22 | C12 | B12 | ||
| 23 | D13 | B13 | ||
| 24 | E12 | B14 | ||
| 25 | A12 | C11 | ||
| 26 | B13 | C12 | ||
| 27 | H13 | B16 | ||
| 28 | G14 | B15 | ||
| 29 | C14 | C13 | ||
| 30 | F13 | C15 | ||
| 31 | E14 | C14 | DACHEALTH See ADC Channel Descriptions. |
ADC
The board includes an Analog Devices AD7928 analog to digital converter. The ADC is located just to the right and slightly below the FPGA. It is labelled U4.
Power Details
The ADC is powered by the +5V power island, which is regulated by an off-board power supply and decoupled near the ADC. It also requires a precise (±1%) 2.5V reference to which it compares voltages when converting from analog to digital. Since the +5V power source is not used for comparison, it is flexible and may vary by ±0.25V without affecting ADC precision.
Setting the Measuring Range
The measuring range is set programmatically by the FPGA over the SPI bus. The way the ADC is connected on the digital board requires that its measuring range be set to 5V, so the RANGE bit should be set to 1 by the FPGA (see Analog Devices documentation).
Data Interfacing
The ADC uses an SPI bus to communicate with the FPGA. This bus is shared with the temperature sensor. SPI related pins include SCLK, CS, DIN, and DOUT. See the Pinout Table below.
Channel Descriptions
This table shows what signals are monitored by the ADC.
| ADC Channel # | ADC Pin # | Net Name | Description |
| VIN0 | 16 | AD7928/VHEALTH | This net helps to monitor to overall health of power on the board, but is specifically intended to monitor -5V. It's voltage is the output of a resistor divider between the +5 and -5V power supplies, with resistor values of 33.2K, and 100K. Assuming +5V and -5V are both correct, the output of the divider will be +2.51V. A reading of other than 2.51V indicates a problem with one of the power supplies. Problems with the +5V power supply can be ruled out by reading VIN3. Based on the reading from VIN3, the voltage of the -5V supply can be calculated. |
| VIN1 | 15 | AD5535/CATHODE | This is the thermal diode output from the DAC. Should read 4.35V (typical) at 25°C. Drops 2.20mV/°C. |
| VIN2 | 14 | +3.3V | This is the +3.3V power plane. A reading of other than +3.3V indicates a problem with VR1. |
| VIN3 | 13 | +5V | This is the +5V power island. A reading of other than +5V indicates a problem with the +5V power supply. |
| VIN4 | 12 | ADC_EXT1 | This trace routes to the backplane via Eurocard pin A7. It is intended to measure the output of thermistor on the amplifier board. |
| VIN5 | 11 | +1.2V | This is the +1.2V power island. This island powers the internal logic of the FPGA. A reading of other than 1.2V indicates a problem with VR3. |
| VIN6 | 10 | ADC_EXT2 | This trace routes to the backplane via Eurocard pin A8. It is intended to measure one of the transistor base voltages on the amplifier board. |
| VIN7 | 9 | DACHEALTH | This channel monitors the output of a resistor divider connected to channel 31 of the DAC. The divider consists of three resistors of 200K, 200K, and 10.2K (in order). The ADC reads out the voltage level between the second 200K and then 10.2K resistor. These resistors were selected so that at 200V, the readout voltage will be 4.973V. Since the divider should be linear, the expected voltage at 20V is 0.4973V. Three resistors were used rather than two to avoid exceeding the resistors' power ratings when the DAC is set to its maximum voltage. Note that since this divider will consume up to 484uA of current at 200V, this DAC channel should not be used for anything that might require more than ~200uA of current (the DAC can source 700uA max). The channel is routed to the backplane nonetheless. |
Pinout Table
| Pin # | Net Name | Description |
| 1 | CLK_5MHZ | SPI clock (SCLK), from FPGA Shared with temperature sensor |
| 2 | DIN | SPI data in, from FPGA Shared with temperature sensor Currently wired wrong |
| 3 | CS | SPI chip select |
| 4 | AGND | |
| 5 | +5V | Power pin |
| 6 | +5V | Power pin |
| 7 | AD7928/REF_IN | +2.5V reference, set by VR2 |
| 8 | AGND | |
| 9-16 | VIN[7:0] | See ADC Channel Descriptions |
| 17 | AGND | |
| 18 | DOUT | SPI data out Currently wired incorrectly |
| 19 | +3.3V | VDRIVE, powers the SPI logic |
| 20 | AGND |
Ethernet Controller
The board uses a Silicon Laboratories CP2201, 28-pin, ethernet controller. The CP2201 is located just above the FPGA, and is labelled U2.
Power Details
The CP2201 uses only +3.3V, which is supplied by the +3.3V power plane and regulated by VR1. Appropriate decoupling capacitors can be found near the CP2201.
Ethernet Jack
To the right of the CP2201 is a Pulse J0011D21NL ethernet jack, labelled J1. This jack has a built-in 1:1 inductive coupling. For best results, connect this jack to a nearby ethernet switch. The jack may also be connected directly to a computer using a crossover cable. Though auto-crossover is not supported by the CP2201, if the computer's NIC supports it, a crossover cable is not necessary to connect directly to a computer.
Ethernet Jack Pins
These are visible only on the back side of the board. Pin 1 is indicated by a square pad. Pin 8 is the farthest pin from pin 1. Pins are numbered such that the 4 pins closer to the plastic thru-hole connectors are odd (1, 3, 5, 7), and the four pins closer to the CP2201 are are even (2, 4, 6, 8).
- Pin 1: TX+
- Pin 2: AC coupled to DGND
- Pin 3: TX-
- Pin 4: RX+
- Pin 5: AC coupled to DGND
- Pin 6: RX-
- Pin 7: No connection
- Pin 8: DGND (direct)
The two large thru-hole pins (not numbered) connect to the metal shielding on the outside of the jack. These are directly connected to DGND to shield against electrical noise inside the jack.
The two plastic thru-hole pins are not conductive and have no electrical connection. They are present only for structural purposes, presumably to prevent stress on the solder points when an ethernet wire is inserted or removed from the jack.
Crystal Oscillator
The CP2201 is responsible for driving the 20MHz crystal oscillator. This oscillator clocks both the CP2201 and the FPGA. The crystal oscillator can be found above the right corner of the FPGA. It can be identified by its four surface mount pads and roughly .3" length. It is labelled Y1, though this label is not visible after the oscillator is soldered on. The CP2201 uses an inverting driver to excite the crystal. The output of the crystal is then sent to the CP2201 and the FPGA.
Bus Format and Multiplexing
The 28-pin CP2201 used on the board only supports multiplexed operation. This means that both address and data information are passed over the same set of 8 traces. Hence, these traces are referred to as the address/data (AD) bus. A separate address line enable (ALE) trace prevents collisions from occuring on these traces. The communication protocol used is the Intel format. See the CP2201's datasheet for more information about this.
Pinout Table
| Pin # | Net Name | Description |
| 1 | CP2201/LA | Link/activity indicator Routed to backplane but not implemented See CP2201 data sheet for information on how to connect to an LED |
| 2 | DGND | By the data sheet, this pin should be AGND We deliberately set it to DGND to avoid noise on AGND plane |
| 3 | +3.3V | AV+ power pin |
| 4 | CP2201/RX- | Connects to RX- on ethernet jack |
| 5 | CP2201/RX+ | Connects to RX+ on ethernet jack |
| 6 | CP2201/TX+ | Connects to TX+ on ethernet jack |
| 7 | CP2201/TX- | Connects to TX- on ethernet jack |
| 8 | +3.3V | "VDD" power pin |
| 9 | DGND | "DGND1" per the data sheet |
| 10 | CP2201/RESET | "RST" per the data sheet Connects to FPGA - should be programmatically triggered upon reset of FPGA by RESET jumper |
| 11-18 | CP2201/AD[0:7] | Bits 0-7 of the address/data bus Connect to FPGA |
| 19 | +3.3V | "VDD" power pin |
| 20 | DGND | "DGND2" per the data sheet |
| 21 | CP2201/ALE | Address line enable Connects to FPGA See CP2201 documentation |
| 22 | CP2201/RD | Read strobe for AD bus Connects to FPGA See CP2201 documentation |
| 23 | CP2201/WR | Write strobe for AD bus Connects to FPGA See CP2201 documentation |
| 24 | CP2201/CS | Chip select Connects to FPGA |
| 25 | CP2201/INT | Interrupt request Connects to FPGA |
| 26 | DGND | "MOTEN" (Motorola enable) per the datasheet Tied low to disable Motorola bus format (enable Intel format) |
| 27 | CP2201/XTAL2 | Crystal oscillator driver The CP2201 inverts the 20MHz clock signal and feeds it back to the crystal oscillator to encourage larger oscillations |
| 28 | FPGA/CLK_IN | "XTAL1" per the data sheet This is the 20MHz clock input Also connects to the FPGA's clock input |
| 29* | DGND | This is not a pin but rather the base of the CP2201 package. It is connected to the DGND plane for thermal relief |
Eurocard Connector
At the bottom of the control board is the Eurocard connector, labelled P2. The Eurocard connector connects the board to the backplane and also connects the board to its power supplies. The Eurocard has 48 pins arranged in three rows of 16 pins each. Rows B and C are exclusively used to pass SiPM bias voltages to the backplane as described in DAC Channel Mapping. Here is a table describing the purpose of pins in row A:
Row A Pinout Table
Note that when viewing the front side of the board with the Eurocard at the bottom, these pins go from right to left. If you look closely at the pins, you will see that pin A1 has a square pad, unlike the round pads of the others.
| Pin # | Net Name | Description |
| A1 | CP2201/LA | Ethernet link/activity indicator routed to backplane |
| A2 | High voltage input (+210V max) | High voltage input for DAC. See DAC for information about what voltage to input here. |
| A3 | -5V | For DAC |
| A4 | +5V | Powers most things on the board |
| A5 | AGND | |
| A6 | DGND | |
| A7 | ADC_EXT1 | Connects to ADC to monitor voltages on amplifier board See ADC |
| A8 | ADC_EXT2 | Connects to ADC to monitor voltages on amplifier board See ADC |
| A9 | No connection | |
| A10 | No connection | |
| A11 | No conneciton | |
| A12 | ID4 | Location identifier bit 4 Used to identify which backplane board is connected to See FPGA |
| A13 | ID3 | Location identifier bit 3 Used to identify which backplane board is connected to See FPGA |
| A14 | ID2 | Location identifier bit 2 Used to identify which backplane board is connected to See FPGA |
| A15 | ID1 | Location identifier bit 1 Used to identify which backplane board is connected to See FPGA |
| A16 | ID0 | Location identifier bit 0 Used to identify which backplane board is connected to See FPGA |