Specifications

APPENDIX B. IMPLEMENTATION DETAILS 35
B.1.2 Software and Firmware
The firmware is the program that is implemented by the FPGA and that controls all
the activity of the c lock board. The firmware is written in Handel-C/VHDL. After the
compilation of the sources of the firmware one gets a hardware description/implementation.
This description is fitted for the FPGA using a software package called Altera MAX PLUS
II software.
The computer hosting the clock board controls it via a Linux kernel module. This module,
when it is loaded, writes the firmware into the FPGA. So if we need a new behavior for the
clock board, we have to compile a new firmware and then reload the kernel module.
B.2 GPS cards
Currently there are 2 identical GPS cards produced by a German company called Meinberg
- the model is GPS167PCI. The GPS card fits into a PCI slot of the computer. There
are some switches on the card that can enable or disable certain outputs – their state for
normal functioning will be given later. The card has a 9-pin serial port that provides on
some of its pins the 10MHz and the 1Hz PPS signals. These signals are distributed to all
clock cards in a local site using wires and T connectors.
For easier identification, the cards are marked with some numbers (on the w hite label from
the card). The card #1 was use d for the initial test with only one computer. The firmware
from this card was upgraded from version 4.16 to version 4.18.
The card #2 had some problems at the beginning - the 10MHz clock was not available at
the output pin (pin number 4 on the serial connector), so we had to get this signal directly
from the 5pin jumper block located near the board bus connector.
NOTE: There is a mistake in the manual - the pin number 1 is located near the bus
connector, not pin number 5.
For the system to work properly, the switches on the cards must have the following config-
uration:
• switch 10 - ON (10MHz clock on pin 4)
• switch 4 - ON (1Hz pulse on pin 8)
• all other - OFF
You can also enable the time capture inputs of the GPS boards (switches 2 and 3 - ON).
After this, a falling TTL slope at one of the inputs (pins 6 or 7) lets the microprocessor
save the current real time in its capture buffer. You can use the program mbgtools-lx-
0.2.3-beta/mbggpscap/mbggpscap to see the data from this buffer.
The firmware on the GPS card can be upgraded when new version are provided by the
manufacturer.