Xilinx has been gaining popularity has it continues to design more FPGA devices. FPGA programming offers a lot of benefits in the technology world. This device helps to offload tasks to hardware and as such boost performance. FPGA is referred to as an integrated circuit programmed for a particular purpose.
Xilinx has designed several FPGA devices. The Xilinx Spartan 5 is a good example of such devices. Also, the Spartan series was birthed as a result of FPGA design experience and feedback from customers. The Spartan series has been able to deliver the major featured needed by ASIC. In this article, we will focus mainly on Xilinx Spartan 5.
What is Xilinx Spartan 5?
The Xilinx Spartan series have a programmable architecture of Configurable Logic Blocks, surrounded by programmable Input/Output Blocks (IOBs). Users can customize this device by loading configuration data into internal static memory cells.
The use of advanced semiconductor technology and architecture helps Xilinx Spartan 5 to achieve low-cost and high-performance operation. Also, Spartan 5 offers single-port and dual-port RAM and fast carry logic. Spartan 5 provides a cost-effective solution while ensuring leading-edge performance.
Xilinx Spartan series integrates a standard FPGA structure. Therefore, this FPGA features an array of CLBs placed in routing channels. Also, a set of input/output blocks helps to achieve the input and outputs f signals. Therefore, this creates a ring around the routing channels and CLBs.
The Configurable Logic Blocks (CLBs) of Xilinx Spartan 5
The configurable logic blocks implement the logic in an FPGA. A CLB can implement any of these functions:
- Functions of about nine variables
- Any function of about four variables and any second function of about four unrelated variables. Also, any third function of about three unrelated variables.
- Any function of four variable with some functions of six variables
- Any single function of five variables
Integrating wide functions in a single block minimizes both the delay in the signal path and the number of blocks needed. Therefore, this helps to achieve both increased speed and capacity. Also, the flexibility of the CLB function generators helps to enhance system speed. Furthermore, this flexibility helps to enhance cell usage.
Each CLB features two flip-flops used for storing the function generator outputs. Also, you can the function generators and flip-flops independently.
You can use the CLB input DIN as a direct input to any of the two flip-flops. The two flip-flops feature set/reset inputs, common clock, and clock enable. You can configure the CLB storage elements as latches. Also, the two latches feature clock enable (EC) inputs and common clock (CK).
The EC is active high. Also, both flip-flops can share the EC line in a CLB. If any of the flip-flop disconnects, the EC for that flip-flop goes back to an active state. Clock enable isn’t invertible within the configuration logic block. Also, the EC is synchronous to the clock and hold timing ascertained for the device.
The CLB’s input comprises four signal control multiplexers. Also, these multiplexers enable you to drive the internal CLB control signals from any of the general control inputs. Any of these inputs is capable of driving any of the four internal control signals.
The Input/Output Blocks (IOBs) of Xilinx Spartan 5
The input/output blocks (IOBs) offer the interface between the internal logic and external package pins. Also, each IOB regulates one package pin. Also, you can configure each IOB for output, input, and bidirectional signals.
You can configure the input signal to the input/output block to directly go to the input register or routing channels. Also, you can program the input register as a level-sensitive latch or an edge-triggered flip-flop.
The output signals can invert within the I/O block and can directly pass to the output buffer. Also, an active High 3-state signal can place the output buffer in a state of high-impedance. Therefore, it can implement 3-state outputs. You can invert the output 3-state (T) signals and the output (O). Also, these signals’ polarity can be independently configured for every IOB.
Routing Channels of Xilinx Spartan 5
In Xilinx Spartan 5 features internal routing channels. All of these channels comprise metal segments with switching matrices and programmable switching points to implement desired routing. Also, there is a structured hierarchical matrix of routing channels. These channels help to achieve automated routing.
The routing channels features
- CLB routing channels that run along every column and row of the CLB array.
- Global routing that features dedicated networks designed to disperse clocks throughout the device with minimum skew and delay. Also, global routing is ideal for other high-fanout signals.
- IOB routing channels which create a ring around the CLB array. Also, it links the I/O with the CLB routing channels.
There are three interconnects that generate the routing channels around the CLB. These interconnects are longlines, double-length, and single-length. There is a signal steering matrix at the intersection of every horizontal and vertical routing channel. The single length lines offer the best interconnect flexibility. Also, they provide fast routing between adjacent blocks.
Advanced Features of Xilinx Spartan 5
The boundary scan
The traditional method of testing electronic assemblies is the “bed of nails.” As a result of closer pin spacing, this method has become less appropriate. The Spartan 5 family implements IEEE 1149.1-compatible BYPASS and EXTEST boundary scan instructions.
Master serial mode
This mode utilizes an internal oscillator to produce a Configuration Clock for driving possible slave devices. The configuration clock speed is selectable as 8 MHZ or 1 MHz. Also, configuration always begins at the default slow frequency and then switched to the greater frequency during the first frame.
Serial daisy chain
You can connect multiple devices with various configurations together in a daisy chain. You can wire the configuration clock pins of all devices to configure a daisy chain of devices.
Slave serial mode
In this mode, the FPGA gets serial configuration data on the CCLK’s rising edge. Also, an external signal drives the configuration clock input of the FPGA.
The Xilinx Spartan 5 is a high-volume FPGA that offers all major requirements for ASIC replacement. Also, these requirements include on-chip RAM which is equivalent to ASIC devices.