Driver circuitry for programmable logic devices

[0002] This application claims the benefit of U.S. provisional patent application Ser. No. 60/122,788, filed Mar. 4, 1999, and U.S. Ser. No. 60/142,516, filed Jul. 6, 1999, both of which are hereby incorporated by reference herein in their entireties.

[0003] This invention relates to programmable logic integrated circuitry devices, and more particularly to driver circuitry for use in such devices.

[0004] As is well known to those skilled in the art, programmable logic devices typically include many regions of programmable logic and programmable interconnection resources for selectively conveying signals to, from, and between the logic regions. Each logic region is programmable to perform any of several relatively simple logic operations on input signals applied to the logic region in order to produce one or more logic region output signals. The interconnection resources are programmable to interconnect the logic regions in any of many different configurations so that very complex logic tasks can be performed by concatenating the logic regions in various ways.

[0005] Examples of programmable logic devices are shown in Cliff et al. U.S. Pat. No. 5,689,195, Cliff et al. U.S. Pat. No. 5,909,126, Cliff et al. U.S. Pat. No. 5,963,049, Jefferson et al. U.S. Pat. No. 6,215,326, and Ngai et al. U.S. patent application Ser. No. 09/516,921, filed Mar. 2, 2000, all of which are hereby incorporated by reference herein in their entireties.

[0006] At various locations in the interconnection resources of programmable logic devices signals may need to be strengthened in order to propagate along a relatively long interconnection conductor or to continue to propagate along such a conductor or succession conductors. Such signal strengthening is variously referred to as buffering, re-buffering, driving, or the like, and it may be produced by circuit elements that are variously called buffers, drivers, tri-state drivers, or the like. In general, these various terms are used interchangeably herein. There are many different places in a programmable logic device at which signal buffering may be needed. For example, the output signal of a logic region may need buffering to enable it to better drive an interconnection conductor. A signal reaching the end of an interconnection conductor segment may need to be buffered so that it can drive the next interconnection conductor segment. A signal turning from a horizontal interconnection conductor segment to a vertical interconnection conductor segment (or vice versa) may need to be buffered so that it can drive the receiving segment. Signals received by the device from external circuitry may need buffering, and signals that will be output signals of the device may need buffering in order to drive external circuitry.

[0007] Heretofore the driver circuitry needed in each circuit context has generally been designed specifically for that context. This can lead to a proliferation of buffer circuit designs, which can in turn increase the difficulty of laying out and otherwise designing a new programmable logic device.

[0008] In view of the foregoing, it is an object of this invention to improve and simplify the design of programmable logic devices.

[0009] It is a more particular object of this invention to provide improved and simplified (e.g., by virtue of being more standardized) driver circuitry for programmable logic devices.

[0010] These and other objects of the invention are accomplished in accordance with the principles of the invention by providing a driver circuit module for programmable logic devices, which module can be adapted to perform any of several different tasks, and which module can therefore be used in any of several different contexts in a programmable logic device. The generalized driver module of this invention has the capability of driving a signal from any of several sources (e.g., an adjacent region of programmable logic or adjacent ends of interconnection conductors) to any of several destinations (e.g., adjacent ends of interconnection conductors). Each instance of the driver module on the programmable logic device is hardware-configurable to meet the requirements of that particular instance. For example, the hardware configuration or hardware programming of an instance of the driver module may include providing the metal in the module needed to complete certain connections while omitting the metal needed for other connections.

[0011] Another aspect of the invention relates to the manner in which driver modules, interconnection conductors, and logic regions are disposed on a programmable logic device and inter-related. In this aspect the driver modules can be either the hardware-configurable modules described briefly in the preceding paragraph, or they can be software-programmable driver modules (e.g., of known design). A plurality of logic regions are disposed on the programmable logic device in a row. A plurality of interconnection conductor channels extend along the row. The interconnection conductors in each of the channels are interrupted at spaced locations along the row by driver modules. Each driver module is adjacent a respective one of the logic regions and can drive a signal from the adjacent logic region or the conductors interrupted by that driver module onto some or all of the conductors interrupted by that module. The modules in the various channels are preferably offset from one another along the row. The spacing of the spaced locations in each channel is preferably uniform for all channels and equal to the spacing between logic regions that are separated from one another by several other logic regions. This spacing is also preferably an optimal or at least desirable spacing for re-buffering signals that must be propagated more than one conductor-segment-length along a conductor channel. The driver modules are preferably the sole means by which signals can be driven onto the conductors. This arrangement of logic regions, interconnection conductors, and driver modules has a great many advantages such as improving signal propagation timing uniformity and predictability.

[0012] Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments.

[0013] FIG. 1 is a simplified schematic block diagram of an illustrative embodiment of a driver module in accordance with the invention.

[0014] FIG. 2ais a simplified schematic block diagram showing a first illustrative customization of the module of FIG. 1 in accordance with the invention.

[0015] FIG. 2bis similar to FIG. 2abut shows a second illustrative customization of the FIG. 1 module in accordance with the invention.

[0016] FIG. 2cis again similar to FIG. 2abut shows a third illustrative customization of the FIG. 1 module in accordance with the invention.

[0017] FIG. 2dis once again similar to FIG. 2abut shows a fourth illustrative customization of the FIG. 1 module in accordance with the invention.

[0018] FIG. 2eis similar to FIG. 2dbut shows yet another illustrative customization of the FIG. 1 module in accordance with the invention.

[0019] FIG. 3 is a simplified schematic block diagram of another illustrative embodiment of a driver module in accordance with the invention.

[0020] FIG. 4 is a simplified schematic block diagram of representative portions of an illustrative embodiment of a programmable logic device constructed in accordance with the invention.

[0021] FIG. 5 is generally similar to FIG. 4 but illustrates other possible aspects of the invention.

[0022] FIG. 6 is a simplified block diagram of an illustrative system employing a programmable logic device in accordance with the invention.

[0023] An illustrative embodiment of a driver module 10 in accordance with this invention is shown in FIG. 1. Module 10 includes driver circuitry 20, input selection circuitry 30 for selecting any one of several input signals 32a, 32b, and 34 for application to the input terminal of driver circuitry 20, and output routing circuitry 40 for routing the output signal of driver circuitry 20 to either or both of two output leads 42aand 42b. Driver module 10 also includes four interconnection areas 50a-50d. Within each of these areas 50 each lead 32/52/54 or 42/52/54 extending to the area is connectable to either one or both of the other leads extending to that area. Leads 54aand 54bare bridge connections extending between interconnection areas 50a/50cand 50b/50d, respectively.

[0024] Driver module 10 has many possible uses within a programmable logic device. For example, each of leads 52a-dmay be a different interconnection conductor of the programmable logic device. Thus lead 52amay be a relatively long horizontal interconnection conductor extending to the left from module 10; lead 52bmay be a relatively long horizontal interconnection conductor extending to the right from module 10; lead 52cmay be a relatively short horizontal interconnection conductor extending to the left from module 10; and lead 52dmay be a relatively short horizontal interconnection conductor extending to the right from module 10. Lead 34 may receive an output signal from a region of programmable logic adjacent to module 10.

[0025] In the design of a programmable logic device, driver modules generally like module 10 can be placed anywhere that driver capabilities supportable by such a module are needed. Thereafter in the design of the programmable logic device, each of these generalized driver modules 10 can be customized to provide the connections needed at that particular driver module instance. This customization of each driver module includes making appropriate hardware connections to the module and configuring the hardware of the module in the manner appropriate to the task it must perform. For example, appropriate interconnection conductors may be used for leads 52, and an appropriate logic region output signal may be used for lead 34. Similarly, the hardware represented by elements 30 and 40 is configured to make the desired input and output connections to and from driver circuitry 20. The hardware represented by each of elements 50 is also configured to make the desired connections among the leads to that element. In certain cases elements that are completely unneeded may be omitted. For example, one or both of conductors 54a/bmay be omitted if not needed, or some of elements 50 may be similarly omitted. In the design and fabrication of the programmable logic device that uses driver module 10, different metal connection selections may be made for the various instances of module 10 to hardware-customize each instance of the module as is appropriate for that instance.

[0026] Examples of specific hardware versions of generalized driver module 10 are shown in FIGS. 2a-2e. For example, FIG. 2ashows hardware-configuration of a driver module 10afor use in driving relatively long left- and right-extending horizontal interconnection conductors 52aand 52bfrom a logic region output connected to lead 34. In this example the hardware of element 30 is configured to apply the signal on lead 34 to the input of driver circuitry 20; the hardware of element 40 is configured to apply the output signal of driver circuitry 20 to both of leads 42; and each of areas 50aand 50bis configured to connect the associated leads 42 and 52. Elements of generalized driver module 10 that are not used in FIG. 2aare omitted from that FIG. and can be similarly omitted from the actual circuitry of the programmable logic device for this instance of the driver module if desired.

[0027] FIG. 2bshows an example of customization of the hardware of a driver module 10 for use of the module to drive relatively long left- and right-extending horizontal interconnection conductors 54aand 54bfrom relatively short left-extending horizontal interconnection conductor 52c. Thus in customized driver module 10bthe hardware represented by elements 50cand 30 is configured to apply the signal on conductor 52cto the input terminal of driver circuitry 20, and the hardware represented by elements 40, 50a, and 50bis configured to apply the output signal of driver circuitry 20 to both of conductors 52aand 52b. Again, elements of generalized driver module 10 that are not used in customized driver module 10bare not shown in FIG. 2band can be omitted from the programmable logic device for this instance of the driver module if desired.

[0028] FIG. 2cshows an example of customization of the hardware of a generalized driver module 10 for use in re-buffering the signal from relatively long left-extending horizontal conductor 52afor application to relatively long right-extending horizontal conductor 52b. In this instance the hardware represented by elements 50a, 50c, and 30 is configured to apply the signal on conductor 52ato the input terminal of driver circuitry 20 via leads 54aand 32a. Similarly, the hardware represented by elements 40 and 50bis configured to apply the output signal of driver circuitry 20 to conductor 52bvia lead 42b. (If desired to improve the driving capability, the circuitry shown in FIG. 2ccan be further configured as indicated by the dotted line connection 42ato connect both output legs of the circuitry represented by element 40 to conductor 52b.) Once again, elements of the generalized driver module 10 that are not used in FIG. 2care omitted from that FIG. and can be similarly omitted from the programmable logic device for instances of customized driver module 10cif desired.

[0029] FIG. 2dis similar to FIG. 2cexcept that it shows hardware-configuration of a driver module for use in bi-directional re-buffering between two relatively long horizontal conductors 52aand 52b.

[0030] FIG. 2eis similar to FIG. 2dexcept that it shows hardware-configuration of a driver module as what may be called a “tri-directional” buffer 10e. Buffer 10eacts like a bi-directional buffer (as in FIG. 2d), plus a logic input via lead 34 can reach either or both of the left and right routing 52aand 52b.

[0031] FIG. 3 shows an alternative embodiment of a generalized driver module 100 in accordance with the invention. Driver module 100 has all the same (or similar) elements that driver module 10 has. In FIG. 3 those elements that are essentially repeated from FIG. 1 have the same reference numbers that are used in FIG. 1. In addition to those elements, however, driver module 100 also has other elements. These additional elements have reference numbers in the 100 series. The additional elements of driver module 100 enable that module to additionally serve other interconnection conductors. For example, conductor 162amay be an upwardly extending vertical interconnection conductor on a programmable logic device, and conductor 162bmay be a downwardly extending vertical interconnection conductor on the device. Each of elements 160aand 160bmay be similar to any of above-described elements 50. Leads 144 and 164bare additional output connections from element 40, while leads 146 and 164aare additional inputs to element 30.

[0032] With the addition of possible connections to vertical interconnection conductors 162, driver module 100 can be hardware-customized to perform still more tasks. For example, driver module 100 can be used to drive the output signal 34 of a logic region onto one or both of vertical conductors 162aand 162b.

[0033] Alternatively, driver module 100 can be used to drive a signal from any of horizontal interconnection conductors 52a-donto either or both of vertical interconnection conductors 162aand 162b. As still another alternative, driver module 100 can be used to drive a signal from either of vertical interconnection conductors 162 onto any or all of horizontal conductors 52a-d. Or driver module 100 can be use for uni-directional re-buffering in either direction between vertical interconnection conductors 162, or for bi-directional re-buffering between those two vertical interconnection conductors. Whatever the task to be performed by any instance of driver module 100, the hardware of the various elements of that driver module instance are configured appropriately to that task in the same general way that various exemplary instances of driver module 10 are customized in FIGS. 2a-2e.

[0034] Although leads 34 are illustratively described above as conveying logic region output signals, leads 34 may be alternatively used for other types of signals such as input signals from circuitry that is external to the device that includes the driver modules or from other interconnection conductors on the device. Similarly, one or more of leads 52 or 162 may convey input and/or output pin signals of the device.

[0035] Another aspect of the invention is illustrated by FIG. 4. This FIG. shows a representative portion of programmable logic and programmable interconnection circuitry on a programmable logic device 230. In particular, FIG. 4 shows several representative regions of programmable logic 210 in one representative row of such regions on device 230. FIG. 4 also shows horizontal interconnection conductors 220 that are associated with the depicted row of logic regions 210 and that are provided for conveying signals to, from, and/or between the logic regions in the row. Each of diamonds 200 represents one or more instances of driver modules 10 or 100 or any other suitable driver circuitry. Each of logic regions 210 can receive input signals from any of the adjacent conductors via programmable logic connectors 250 and region-feeding conductors 252. (Only a very few representative ones of elements 250 and 252 are shown in FIG. 4 to avoid over-crowding the drawing.)

[0036] Each logic region 210 produces one or more output signals (i.e., M output signals in the general case) which are applied to N instances of driver modules 200 that are associated with that logic region. For example, logic region 210a1 produces M output signals that are applied to N instances 200a1 of the driver module. N is typically at least equal to M so that each logic region output signal is applied to at least a respective one of driver modules 200. Preferably N is greater than M so that each logic region output signal can be applied to a respective two or more instances of driver module 200. There may also be some overlap between the instances of driver modules 200 that are used for each logic region output signal. In other words, a driver module 200 may receive more than one of the associated logic region output signals. (For ease of reference herein it is assumed that M and N are both greater than one, although it will be understood that M can be one and that N can also be one if desired.)

[0037] Each instance of a driver module 200 is disposed between a leftward extending horizontal interconnection conductor 220 and a rightward extending horizontal interconnection conductor 220. For example, each instance of driver module 200a1 is disposed between one of N horizontal conductors 220 extending to left from driver modules 200a1 and one of N horizontal conductors 220 extending to the right from those driver modules.

[0038] The driver modules 200 associated with each of logic regions 210 are located in the same layout tile. Thus, when, in the design of a device that uses the FIG. 4 circuitry, tiles are “copied and pasted” to form rows of regions 210, driver modules 200 are automatically evenly distributed across each row. These hardware-configurable driver modules can then be metal-configured differently to meet the different requirements in different regions. In the depicted embodiment the pattern of driver modules 200 repeats after eight horizontally adjacent logic regions 210. Thus each conductor 220 extends from a driver module 200 past seven adjacent logic regions 210 before encountering another driver module 200 associated with an eighth adjacent logic region 210. As a specific example of this consider a conductor 220elocated near the center of FIG. 4. Such a conductor extends to the right from a driver module instance 200e1 past logic regions 210f1, 210g1, 210h1, 210a2, 210b2, 210c2, and 210d2 to a driver module instance 200e2.

[0039] The effect of the pattern of driver modules 200 and conductors 220 shown in FIG. 4 is to make all of conductors 220 the same length between horizontally adjacent driver modules. This conductor length can be chosen to be the optimal length for a conductor before the signal on that conductor needs to be re-buffered. With an arrangement of the type shown in FIG. 4 it is known that each logic region output signal is always driven onto the end of a conductor segment 220. It is also known that the remote end of that conductor segment 220 is a fixed distance away from the input end and that a re-buffering driver module 200 is available at that remote end for re-buffering the signal onto another horizontally adjacent segment if the signal needs to be propagated beyond the circuitry reachable from the first segment.

[0040] As a specific example of the foregoing, consider an output signal from logic region 210e1. Such a signal can be applied to the left-hand end of a conductor segment 220eextending to the right from a driver module 200e1. The signal on that conductor segment 220ecan be applied to any of the logic regions 210f1-210d2 (and possibly also 210e1 and 210e2) by logic-region-feeding conductors like conductors 252. At the right-hand end of the conductor segment 220ebeing discussed that conductor segment encounters a driver module 200e2. If the signal on the conductor segment 220ebeing discussed is needed by logic regions 210 farther to the right, the immediately abovementioned driver module 200e2 can be used to re-buffer that signal and to apply the re-buffered signal to another conductor segment 220eextending to the right from that driver module.

[0041] Because the starting point of the signal on each conductor segment 220 is always adjacent one end of that segment, because the conductor segments are of known length, because a driver module 200 is available at each end of each segment, and because the conductor segment lengths are selected so that a signal traversing the length of a conductor segment will be in need of re-buffering as it reaches a driver module 200 capable of providing that re-buffering, an arrangement of elements like that shown in FIG. 4 helps make signal propagation throughout device 230 more uniform and predictable. In addition, once a signal is on a conductor segment 220, it is known that the signal is available to a substantial number of logic regions 210 (i.e., all the logic regions passed by that conductor segment) without any further driver delays being introduced into at least that much propagation of the signal. All of these considerations facilitate reliable, high-speed operation of device 230.

[0042] It will be appreciated that adjacent the edges of device 230 some of conductor segments 220 will have to be made shorter than the length otherwise used for such segments. However, at these locations bi-directional re-buffering capabilities may not be needed. Accordingly, instances of driver modules 200 adjacent the edges of device 230 can be hardware-configured as tri-state drivers (e.g., for selectively driving signals from input pins, input/output pins, or adjacent logic regions 210 onto conductor segments 220, or for selectively driving signals from such conductor segments 220 onto output or input/output pins). FIG. 5 shows an example of inclusion of such tri-state drivers 240 near edges of device 230. FIG. 5 also shows relatively short edge segments of conductors 220 short-circuited to the adjacent longer segments of those conductors to eliminate the overhead of re-buffering for very short segments of wire. This short-circuiting is shown for the two lower left and two upper right conductor groups in FIG. 5. These are also the conductor groups shown with tri-state drivers 240.

[0043] Some of the advantages of the circuitry of this invention are as follows: 1. it eliminates delay overhead of crossing fixed re-buffering or hierarchical boundaries; 2. it provides optimal buffering from source and destination points, whether the destination point is before or after several staggered drivers; 3. it provides higher noise immunity because it allows shielding of signal drivers from unused wires and also shields from unused diffusion loading; 4. it decreases routing channel requirements when unstitched metal lines (e.g., horizontally adjacent conductor segments 220) can be used independently; and 5. it can improve speed by re-distributing fan-out (because non-critical paths can be off-loaded by turning onto another driver using a lead 34 to convey a signal from one interconnection conductor to another).

[0044] FIG. 6 illustrates a programmable logic device 300 constructed in accordance with the present invention in a data processing system. Thus device 300 may be constructed using hardware-configurable driver modules like those shown in FIGS. 1-3 and/or with driver module arrangements like those shown in FIGS. 4 and/or 5. Data processing system 302 may include one or more of the following components: a processor 304; memory 306; I/O circuitry 308; and peripheral devices 310. These components are coupled together by a system bus 320 and are populated on a circuit board 330 which is contained in an end-user system 340.

[0045] System 302 can be used in a wide variety of applications, such as computer networking, data networking, instrumentation, video processing, digital signal processing, or any other application where the advantage of using programmable or reprogrammable logic is desirable. Programmable logic device 300 can be used to perform a variety of different logic functions. For example programmable logic device 300 can be configured as a processor or controller that works in cooperation with processor 304. Programmable logic device 300 may also be used as an arbiter for arbitrating access to a shared resource in system 302. In yet another example, programmable logic device 300 can be configured as an interface between processor 304 and one of the other components in system 302. It should be noted that system 302 is only exemplary, and that the true scope and spirit of the invention should be indicated by the following claims.

[0046] It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. For example the driver modules 200 used as shown in FIGS. 4 and 5 do not have to be the hardware-configurable driver modules shown in the earlier FIGS. Instead, driver modules 200 can be programmably controlled driver circuits (e.g., those shown in FIG. 8 of Reddy et al. U.S. Pat. No. 5,977,793, which is hereby incorporated by reference herein in its entirety).

[0047] Most programmable logic devices have more than one row of logic regions, thereby creating a two-dimensional array of intersecting rows and columns of logic regions. Vertical interconnection conductors (like conductors 162 in FIG. 3) may be associated with the columns of logic regions, and a vertically offset or staggered driver module pattern analogous to the horizontally offset or staggered patterns shown in FIGS. 4 and 5 may be alternatively or additionally employed in the vertical interconnection conductors.

[0048] It will be understood that various directional and orientational terms such as “vertical” and “horizontal”, “left” and “right”, “row” and “column”, and the like are used herein only for convenience, and that no fixed or absolute directional or orientational limitations are intended by the use of these words. For example, the devices of this invention can have any desired orientation. If reoriented, different directional or orientational terms may need to be used in their description, but that will not alter their fundamental nature as within the scope and spirit of the invention.

[0049] It will also be understood that any suitable logic can be used in logic regions 210. For example, sum-of-products logic, look-up table logic, or any other type of logic can be used. Similarly, any of many different technologies can be used to make devices in accordance with the invention. Examples of suitable technologies include EPROMs, EEPROMs, pass transistors, transmission gates, fuses, antifuses, laser fuses, metal optional links, SRAMs, DRAMs, FIFO memories, function control registers (e.g., as in Wahlstrom U.S. Pat. No. 3,473,160), ferro-electric memories, and the like. The programmable logic devices of this invention can be one-time-only programmable or reprogrammable.