CA2392503A1 - Computer module and motherboard - Google Patents

Abstract

A single board computer module (102) is provided with an FPGA (107) which is arranged to adjust the bus mapping and functions from a CPU (103) to the required bus connections (105) of a motherboard (101). The module can be arranged to serve the required bus connections and to adjust the bus mapping accordingly.

Description

WO 01/3899? PCT/GB99103946 COMPUTER MODULE AND MOTHERBOARD
The present invention relates to a computer module (particularly but not exclusively when in the form of a daughterboard), to a motherboard for such a daughterboard and to a control arrangement comprising the daughterboard and motherboard in combination.
In preferred embodiments the daughterboard is a. single-board computer (SBC) in which all the essential computer components required to perform the desired computer functions are substantially contained on a single printed wiring module or board. The heart of such a machine is one or more central processing units (CPUs) or micro processor units (MPUs). The CPU controls the operation of the machine and performs various types of input/output (I/O) operations, calculations and logical operations in accordance with computer program instructions. In order to do so, the CPU is generally supported by memory and I j0 circuits on the printed wiring module.
Single-board computers are often adapted for specific functions. For example, they may be used as controllers for other machines or systems, and SBCs are often designed with this flexibility in mind. Included in the memory is a portion which is typically but not necessarily read-only, and which contains a set of customised program instructions directing the CPU to perform the specific task for which the SBC is adapted. However, the flexibility afforded by reprogramming may not be adequate to adapt current SBCs to all the tasks to which they may otherwise be successfully applied because for sufficiently different tasks, different CPUs, memory types and sizes and support logic devices may be desirable. Yet, designers ordinarily cannot readily swap one CPU sub-system for another CPU sub-system better suited to a specific application or needs of a user.
Therefore, one solution to this problem has been to locate the CPU, memory, support logic devices and I/O circuits (or other suitable combination) on a small daughtercard and the application specific funedons on a motherboard. In order to interconnect daughtercards carrying different CPU sub-systems to a common motherboard design, prior art technology requires that a standard electrical interconnection be designed and implemented. Applications having other than the standard electrical interconnection as their native irxterconnection scheme would be adapted by logic on the motherboard to interface with the signals of the standard daughtercard. However, this approach has the disadvantage of requiring a sometimes significant amount of logic circuits to be present on the motherboard to perform the adaptation and service the standard CPU and daughtercard interface.
It should be noted that the above described problem in the prior art may also arise in computer systems other than SBCs wherein a flexible system is desired which includes the capability of swapping CPU sub-systems among CPLI sub-systems of different types.
US 5898846 (Kelly) discloses a computer module comprising a CPU or microprocessor coupled to local memory, the module further comprising bus connector means far connecting the module to an external bus.
However, the above module requires a specific motherboard having an FPGA or other electronic switching means.

WO 01/38997 PCTlGB99/03946 An object of the present invention is to provide a computer module that is not subject to this requirement.
Accordingly, in one aspect the invention provides a computer module characterised by electronic control means arranged to modify and/or re-route inputs and/or outputs of the CPU or microprocessor to conductors of the connector means in accordance with stored configuration information.
For example, the inputs or outputs could be inverted or their timing could be altered.
Further preferred features are defined in dependent claims.
In another aspect the invention provides a motherboard for such a computer module, the motherboard having a bus for connection to said bus connector means and means for controlling such an electronic control means.
Preferably said means for controlling the electronic control means comprises an electronic configuration device having at least one output line connected to said bus and a memory containing a stored configuration program, the configuration device or electronic control means being arranged to be controlled by the configuration program.
Preferably the motherboard has further circuitry connected to input or output ports on the motherboard for interfacing with external circuitry, said further circuitry having one or more control inputs or outputs coupled to said bus.

In a further aspect the invention provides a control arrangement comprising a daughterboard in accordance with the first mentioned aspect connected to a motherboard in accordance with the second mentioned aspect, the electronic controlling means being arranged to configure the bus connections of the daughterboard to match the bus of the motherboard.
In one embodiment of the present invention, there is provided an interconnect system for a computer, the computer including a CPU sub-system (CPU, memory, support logic and interconnections) and the computer further including application [specific] input/output connections. The interconnect system comprises a programmable logic circuit having a first set of input/output lines connected to the CPU sub-system and a second set of input/output lines connected to the application [specific] input/output connections; and a memory containing a configuration program including instructions to the programmable logic circuit to map the lines of the CPU sub-system to the application [specific] input/output connections and connected such that it programs t:he programmable logic circuit each time a predetermined event occurs.
In another embodiment of the invention, there is provided on a CPU-based daughtercard, including a CPU sub-system, being electrically connected to a programmable logic circuit and the programmable logic circuit also being electrically connected to a connector on the daughtercard. The CPU-based daughtercard comprises a daughtercard connector adapted to mate with the connector included on an application motherboard; a CPU having input/output lines electrically connected to the programmable logic circuit, CPU sub-system and daughtercard connector; memory containing a configuration program for the S
programmable logic circuit; and a programmable logic circuit having lines electrically connected to the daughtercard connector and lines connected to a CPU
sub-system and memory bus wherein loading the configuration program configures the programmable logic circuit to map between the CPU sub-system and memory bus and the daughtereard connector input/ output lines.
In another embodiment of the invention there is provided on a CPU-based daughtercard including a CPU sub-system having a connector electrically connected to a programmable logic circuit, the programmable logic circuit further being electrically connected to a connector on the daughtercard, capable of being connected to an application motherboard. The motherboard comprises a connector adapted to mate with the daughtercard connector; and various circuits to allow the motherboard to perform specific application functions. Such circuits may include peripherals, memory and connectors.
In yet another embodiment of the invention the application motherboard contains configuration hardware to allow the CPU-based daughtercard to self configure;
wherein reading the configuration hardware allows the CPU-based daughtercard to configure the programmable logic circuit to map between the CPU-based daughtercard input/output lines and application motherboard.
In yet another embodiment of the invention, there is provided a CPU
interconnect system for a computer application, the computer including a CPU-based daughtercard having input/output lines disposed on a first module and the computer further including application [specific] input/output connections disposed on a second module. The interconnect system may include elements for connecting the CPU sub-system to the application [specific] input/output connections in accordance with a mapping not fixed in the elements for connecting, disposed on the first module; and elements for loading the mapping in to the elements for connecting, the elements for loading operative upon the occurrence of a predetermined event. The elements for connecting may include such conductors and connectors or sockets as may be required to electrically connect signals from their sources to their destinations.
Variants of each of the above embodiments of the invention are possible. For example, the elements far holding or memory may be any of a variety of types of non-volatile memory, such as read-only memory (ROM), electrically alterable read-only memory (EAROM) such as Flash or EEPROM, non-volatile random access memory (NVRAM) or battery backed up random access memory. The CPU may further be one of a plurality of CPU types. For example, the CPU types supported may include, but not limited to processors of various data and address but widths made by Intel, Hitachi, NEC, AMD, IBM, etc. The mapping held by the elements for holding or memory corresponds to the CPU type and the application interface.
The programmable logic circuit may be a field programmable logic array (FPGA) or other similar programmable circuit. for example, the pro~-ammable logic circuit could be programmable array logic (PAL), an application-specific integrated circuit (ASIC), or other circuit including programmable and reprogrammable logic. The predetermined event may be any convenient event, such as power up or some form of operator intervention.
Preferred embodiments of the invention are described below by way of example only with reference to Figures 1 to 7 of the accompanying drawings, wherein WU 0113899? PCT/GB99/03946 Figure 1 is a schematic block diagram of one CPU-based daughtercard and motherboard in accordance with the invention;
Figure 2 is a schematic block diagram of a daughterboard in accordance with the invention;
Figure 3 is a diagram of the memory contents of the daugktterboard of Figure 2;
Figure 4 is a schematic block diagram of a further daughterboard in accordance with the invention showing an interface connection to configuration information in a memory on a motherboard;
Figure 5 is a diagram of the memory contents of the memory of the daughterboard of Figure 4;
Figure 6 is a schematic block diagram of a further daughterboard in accordance with the invention showing an interface connection to configuration information on a motherboard, and Figure 7 is a diagram of the memory contents of the configuration memory in Figure 6.
In the drawings like reference designations indicate like elements.

Figure 1 illustrates an embodiment of the invention wherein there is provided a daughtercard 102, including a central processing unit CPU) or micro processor unit (MPU) 103, memory 104 and reprogrammable logic 107, connected to a connector 105 on an application motherboard 101 by an edge connector 105a.
Other types of connections could also be used. The application motherboard includes substantially all necessary functions for a particular application, except for the central processing sub-system functions. The central processing sub-system functions required by a particular application are supplied by plugging in the CPU-based daughtercard 102. The interconnection between the CPU-based daughtercard 102 and the motherboard lUl is now described in greater detail.
The CPU-based daughtercard 102 communicates with other components of the application motherboard 101 via signals sent over a plurality of input/output lines 106, 106a and 106b. However, as noted above, different CPUs are defined to have one or more different input/output lines and electrical characteristics.
Therefore, at least some of the connections between the CPU 103 input/output lines and the motherboard are programmable (i.e. input/output lines 106b). In the illustrated embodiment, the CPU-based daughtercard input/output lines are connected to the motherboard through an interface including edge connector 105a on the daughterboard and socket connector 105 on the motherboard. Although in conventional interconnect systems the individual conductors of such connectors would be defined to correspond to specific functions of the CPU-based daughtercard input/output lines 106a and 106b, in this embodiment of the invention the CPU-based daughtercard may be associated with the conductors and connectors associated with input/output lines 106b in any convenient fashion. Thus, if the WO 0113899? PCT1GB99103946 CPU sub-system connections 108 have different physical and electrical properties they may be routed to any conductors of the connector 105 on the daughtercard.
Conversely, if an alternative motherboard with different connections of input/output lines on connector 105, the daughtercard may be routed to different conductors of the connector 105.
In this embodiment of the invention some of the CPU-based daughtercard input/output lines 106b are mapped on to an electronic switching device such as a field-programmable gate array (FPGA) 107. An FPGA is one type of programmable logic circuit device including a collection of general logic devices which may be connected together to form a desired logic function by programming.
Programming usually involves loading a map of interconnections between the general logic devices into the FPGA. The general logic devices are usually serial logic elements, such as gates, but also include parallel and clock elements in many versions. The logic function embodied in a programmed FPGA may be as simple as a routing of signals, such as might be performed by a switch. However, the logic function may include such processing of signals as changing timing or polarity or function, may produce output signals not found among the input signals, or may include complete functional blocks such as universal Asynchronous Receive/Transmitters (DARTS) or Direct memory Access Controllers (DMACs). In use in embodiments of the present invention, the FPGA may be programmed, but not limited to, any or alI
of the tasks noted above.
On being programmed, the FPGA 107 performs the overall logic function necessary to map the collection of functions required by the CPU sub-system connections WO 01138997 PCT/GB99l03946 to the input/output lines 106b of the daughtercard connector 105. For example, a particular CPU 103 may issue memory read and write requests using one set of signals transmitted over the CPU sub-system connections 108, whereas the motherboard connections 106 may include a different set of signals to perform read and write functions in an attached memory 109. The FPGA logic function is thus designed to map between the two distinct representations of a similar function.
Further, the CPU-based daughtercard FPGA Iogic function may configure the input/output lines to conform to standard bus configurations, such as ISA or PCI, bespoke bus configurations such as CPU native, or application motherboard custom connections such as peripherals 111, and include connections to functional blocks within the FPGA.
The motherboard 101 in this embodiment contains additional program memory 109 containing application program information specific to an individual motherboard that can be executed by the CPU or MPU I03 on the daughtercard 102.
The motherboard also contains configuration hardware 110 such as switches, jumpers and resistors that can be read by the daughtercard and allow the daugk~tercard to configure itself according to the configuration hardware information. The motherboard also contains configuration memory 1 12 that can be read by the daughtercard, and which allows the daughtercard to configure itself according to the configuration memory information.
A person or ordinary skill in this art is capable of designing such a mapping given the various signal functions and timing requirements. It should also be evident that although this embodiment employs an FPGA, any similar programmable logic circuit may be used, without regard to whether that circuit resides in a single package or multiple packages.
Figures 2 and 3 show the read-only memory (ROM) 104 and its contents on the CPU-based daughtercard 102. One purpose for this ROM I04 is to hold the program for the FPGA 107. Each CPU 103 is accompanied by a ROM 104 containing a program which properly maps the CPU sub-system connections 108 for the CPU 103 to the application motherboard connector 105 and the motherboard connections 106. Thus in the case of the illustrated embodiment of the invention, when the CPU-based daughtercard 102 including the CPU 103 is plugged into the motherboard 101, the FPGA 107 may be loaded via the CPU sub-system connections 108 with different programs corresponding to the mapping required for different CPUs 103 and motherboards 101.
Figure 3 shows an example memory map for the daughtercard 102. The programs and data of Figure 3 are stored in memory 104 of the daughtercard. When the daughtercard starts executing a program in the ROM 104, it first accesses a Reprogrammable Logic Loader Program 201 which tells the CPU or MPU 103 to program the reprogrammable logic 107 with the information stored in a Reprogrammable Logic Application Interface Image 203 area of memory. When this is completed, the CPU executes the program /and uses data) from the Application Program and Data area 202 of the memory.
The memory 104 provided on the CPU-based daughtercard 102 need not be strictly read-only but should include a non-volatile memory type, Any suitable type of memory which retains its contents while power is not applied to the daughtercard 102 may be employed. Thus, although the program for the FPGA 107 is retained during intervals of power being off, the CPU-based daughtercard 102 could be reprogrammed, when improvements are made to the FPGA program corresponding to the CPU 103 or the application motherboard 101 or a new application or motherboard is produced. Electrically alterable read-only (EAROM) is an example of a memory which is non-volatile and hence, used primarily in a read-only mode, but whose contents may be changed from time to time as required.
Furthermore, holding the program for FPGA 107 need not be the only function of a ROM or similar memory 104 on the CPU-based daughtercard 102. For example, the ROM 104 may include instructions for programming other devices, additional configuration data for use by the CPU 103, or program instructions far one or more CPU functions. Other applications of that space in the ROM 104 which is not used by the FPGA program will become apparent to those designing specific applications.
The FPGA 107 may be loaded with the configuration program contained in the ROM
104 upon the occurrence of any convenient event. For example, the FPGA 107 may be loaded at system power up, or upon issuance of a reset signal as a result of operator intervention. Other automatic and operator intervention events which may be used at appropriate times to load or partially reload the FPGA 107 will be readily apparent to those skilled in the art who may be developing any particular application.
It will be readily apparent to those skilled in this art that the invention may be practised using technologies other than the conventional printed wiring technology involving conventional motherboards and daughtercards in connection with which wo om~~ rcr~cBmoa~~

the invention has been illustrated. For example, the circuitry described above as being associated with a daughtercard may be included in some type of hybrid or other integrated module, including integration onto a single component. The FPGA
107 and connector 105 technologies may be similarly varied, in accordance with generally accepted design techniques. For example, the connectors 105 may simply be a socket into which all hybrid CPU sub-system modules 102 may be designed to fit. Therefore, it is intended that the terms motherboard 101, daughtercard and related terms in this application be broadly construed to include any technology by which the separation of function and connections between those functions discussed above may be accomplished.
Figures 4 and 5 show a further daughterboard. Read-only memory 104 rnay, for example, contain more than one FPGA map, and configuration hardware 110 included on the motherboard show the identification of the type of motherboard 101. This may for example, take the form of switches or wire jumpers or the like, or a memory containing configuration data. The CPU would read this motherboard configuration hardware 110. Upon receipt of a motherboard identification from configuration hardware 110, the CPU-based daughtercard would then correctly and appropriately self configure the programmable logic circuits 107. If no correct identification was found, the CPU-based daughtercard could put itself into a safe state.
Figure 5 shows an example memory map for the daughtercard 102 of Figure 4 which would configure itself based on configuration information from the motherboard 10I (Figure 1). When the daughtercard starts executing a Reprogrammable Logic Configuration Checker Program 301 in the ROM, it first WO 01!38997 PCT/CB99l03946 accesses the motherboard to read the configuration information in the configuration hardware 110 (Figure 1). On the basis of this information the Reprogrammable Logic Loader Program 301 tells the CPU or MPU 103 to program the reprogrammable logic with the correct Reprogrammable Logic Application Interface Image 303, 304, 305 appropriate to the configuration hardware found on the motherboard. When this is completed, the CPU exer_utes the program (and uses data) from the Application Program and Data area 302 of the memory. This example shows 3 configurations stored, but this could be any number appropriate to the number of motherboard configurations required.
Figures 6 and 7 show a further variant of the daughtercard 102. Read-only memory 112, may for example, be on the motherboard. This memory contains Reprogrammable Logic Application Interface Image 401 to be used by the daughtercard 102. The daughtercard Reprogrammable Logic block 107 (suitably an FPGA} reads this memory and then self configures the programmable logic circuits.
Alternatively, the CPU-based daughtercard 102 could retrieve a new Reprogrammable logic Application Interface Image 401 for the FPGA and store this in its own memory 104. The motherboard Configuration memory may contain other information 402 that is needed by the motherboard and daughtercard such as a program or data information.

Claims (16)

1. A computer module (102) comprising a CPU or microprocessor (103) coupled to local memory (104), the module further comprising bus connector means (105a) for connecting the module to an external bus (106) characterised by electronic control means (107) arranged to modify and/or re-route inputs and/or outputs (108) of the CPU or microprocessor to conductors of the connector means in accordance with stored configuration information.

2. A computer module (102) according to Claim 1, wherein the module (102) comprises memory means (104) in which said configuration information is stored.

3. A computer module (102) according to Claim 2, wherein said memory means (104) is non-volatile ROM.

4. A computer module (102) according to Claim 3, wherein said memory means (104) is electrically alterable ROM (EAROM).

5. A computer module (102) according to any preceding claim, wherein the electronic control means (107) is programmable.

6. A computer module (102) according to Claim 5, wherein the programmable electronic control means (107) comprises a field-programmable gate array (FPGA) a programmable array logic (PAL) device, an application-specific integrated circuit (ASIC), a complex programmable logic device (CPLD) or a programmable logic device (PLD).

7. A computer module (102) according to any preceding claim 1, wherein the electronic control means (107) has one or more control input lines coupled to said bus connector means.

8. A computer module (102) according to any preceding claim, wherein the electronic control means (107) has one or more control output lines coupled to said bus connector means.

9. A computer module (102) according to any preceding claim, wherein the electronic control means (107) is arranged to modify and/or re-route said inputs and/or outputs in response to a predetermined event detected via the bus connector means (105).

10. A computer module (102) according to Claim 9, wherein said predetermined event is associated with switching on the module or a command entered by a user.

11. A computer module (102) according to any preceding claim, wherein the electronic switching means (107) is arranged to modify and/or re-route said inputs and/or outputs in dependence upon external electrical conditions detected at the bus connector means (105a).

12. A computer module as claimed in any of Claims 1 to 11, which is in the form of a daughterboard (102).

13. A motherboard (101) for a computer module (102) as claimed in any preceding claim, the motherboard having a bus (106) for connection to said bus connector means (105a) and means (110) for controlling such an electronic control means (107).

14. A motherboard (101) according to Claim 13, wherein said controlling means (110) comprises an electronic configuration device having at least one output line connected to said bus (106) and a memory (112) containing a stored configuration program, the configuration device or electronic control means (110/107) being arranged to be controlled by the configuration program.

15. A motherboard (101) according to Claim 13 or Claim 14, having further circuitry connected to input or output ports on the motherboard (101) for interfacing with external circuitry, said further circuitry having one or more control inputs or outputs coupled to said bus (106).

16. A control arrangement comprising a daughterboard (102) according to Claim 12, connected to a motherboard (101) according to any of Claims 12 to 14, the electronic control means (107) being arranged to configure the bus connections of the daughterboard to match the bus (106) of the motherboard (101).