There are three different types of cables: serial, parallel, and XChecker.
You can use a serial cable only to download configuration data. The serial cable consists of a cable with a 6-lead header connector with the following connections: VCC, GND, CCLK, D/P, PROG, and DIN. It also includes a female RS-232 serial connector.
You can use a parallel cable only to download configuration data. The Xilinx parallel cable consists of a 6-lead flying header connector with the following connections: VCC, GND, CCLK, D/P, PROG, and DIN. It also includes a 25-pin male connector.
The parallel cable is supported on the PC only.
You can use the XChecker cable to download, verify, and debug. The XChecker cable assembly houses internal circuitry consisting of a Xilinx FPGA, which functions as an interface between the XChecker software and the target FPGA; a static RAM, which stores the configuration data for download and readback; and an oscillator circuit, which provides a system clock to facilitate download and readback of configuration data.
Using XChecker requires a standard DB-9 or DB-25 RS-232 serial port and may require a DB9/DB25 adapter.
The XChecker cable has 14 signal connections, plus VCC and GND. It comes with two header connectors and two flying lead connectors. The “XChecker Cable” figure shows top and bottom views of the XChecker cable.
Figure 4.1 XChecker Cable |  |
You can use the XChecker cable with a single FPGA or several connected in a daisy chain to download configuration data. When used to read back data or as a logic probe, the XChecker cable can only be used with one device at a time. The XChecker cable transmits configuration data to all target FPGAs at 921 kHz.
Communication between the host system and the XChecker cable is dependent on host system capability. The “Valid Baud Rates” table lists the valid baud rates for the supported platforms.
| Baud Rate | ||||
|---|---|---|---|---|
| Platform | 9600 | 19200 | 38400 | 115200 |
| Sun | X | X | X | |
| HP | X | X | X | X |
| PC | X | X | X | X |
| X indicates supported baud rate. | ||||
The XChecker hardware is the cable assembly with internal logic as described in the previous section, a test fixture, and a set of headers to connect the cable to your target system. Available as optional equipment is a 3 V Adapter for use with low-voltage parts. The “XChecker Hardware and Accessories” figure shows the XChecker cable hardware and accessories.
Figure 4.2 XChecker Hardware and Accessories | |
The optional 3 V adapter accepts VCC supply voltages from the target system from +2.9 V to +5.25 V. The 3 V adapter contains a voltage step-up circuit that generates the 5 V supply voltage needed by XChecker.
Because the 3 V adapter can accept input voltages up to 5.25 V, there is no need to remove the adapter when moving the XChecker cable between low-voltage systems and higher 5 V systems. Except for the voltage conversion, the 3 V adapter is completely invisible to the XChecker hardware or the target system.
