Implementing Your Applications

You can use the PROM File Formatter to generate a PROM file containing data to configure a single FPGA device, or a PROM file to configure one or more groups of FPGA devices. You can also store multiple data streams in the same PROM file and use these data streams to reconfigure a device or daisy chain for different applications.

The following table summarizes the various ways of structuring a PROM file.

Table 1_1 Configuration Data Stream Combinations

Number of Applications	Number of FPGA Devices to Configure	Number of Data Streams and BIT Files
Single Application	Single device	One data stream with a single BIT file.
	Daisy chain of devices	One data stream with multiple BIT files.
	Multiple daisy chains of devices¹ 1. This type of application can be implemented with a byte-wide PROM only. Each data stream will use a different start-up address in the PROM file.	Multiple data streams with multiple BIT files in each data stream. Each data stream includes configuration data for a different daisy chain of devices.
Multiple Applications (Reprogramming)	Single device	Multiple data streams with a single BIT file in each data stream.
Multiple Applications (Reprogramming)	Daisy chain of devices	Multiple data streams with multiple BIT files in each data stream. Each data stream programs the group of devices for a different application.

The following figure depicts the structure of a byte-wide PROM file loaded in master mode and designed to configure three daisy chains of devices. Data Stream #1 is for a daisy chain of two devices. Data Stream #2 is for a second daisy chain of two devices. Data Stream #3 is for a single device.

Figure 1.4 Configuration Data Streams for Multiple Daisy Chains

Single Application PROM Files

There are three different types of configuration data streams.

Single Device

To implement an application for a single device, use a data stream containing a single BIT file. Data Stream #3 in the “Configuration Data Streams for Multiple Daisy Chains” figure shows a configuration data stream for a single device.
One group of daisy-chained devices

To implement an application for a group of FPGA devices connected together in a daisy chain, use a single data stream containing multiple BIT files, that is, one BIT file for each device in the daisy chain. Data Stream #2 in the “Configuration Data Streams for Multiple Daisy Chains” figure shows a configuration data stream for a single daisy chain of devices.
Several groups of daisy-chained devices

To implement an application for several groups of daisy chained devices, you must build one data stream per daisy chain. The“Configuration Data Streams for Multiple Daisy Chains” figure is an example of a PROM file for multiple daisy chains of devices. This type of implementation is valid for byte-wide PROMs, which can be set for different start-up addresses, or for creating a bitstream for microprocessor download.

Multiple Application PROM Files

The Xilinx SRAM FPGA technology allows you to design multiple applications for a single device or a daisy chain of devices. Each data stream in the PROM description area represents a different configuration or application for the same device or daisy chain of devices.

To implement several applications for a single device, build a PROM file made of several data streams, with each data stream containing a single BIT file. To implement several applications for a group of daisy chained devices, use several data streams containing multiple BIT files. Each data stream programs the group of devices for a different application.

NOTE

The number of BIT files within each data stream must be the same.

Refer to the “Configuration Data Streams for Multiple Daisy Chains” figure for an example of a PROM file designed for multiple applications. In this figure, Data Stream #1 configures the daisy chain of devices with the “Slow” application. Data Stream #2 configures the same daisy chain with the “Fast” application. You can easily switch to the next application by reprogramming the FPGA from a PROM file formatted for multiple applications or from a microprocessor.