JP5010065B2 - Microcomputer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microcomputer incorporating a USB interface circuit and an EEPROM as a program storage memory, and more particularly to a microcomputer having identification information for identifying a supplier of the microcomputer.
[0002]
[Prior art]
In recent years, support for USB (Universal Serial Bus) has been started in personal computers and the like in order to increase the degree of freedom of expandability of peripheral devices. USB is a serial interface standard devised in consideration of user convenience, and can be commonly used for communication between various peripheral devices such as a keyboard, mouse, camera, printer, scanner, and speaker and a personal computer.
[0003]
FIG. 4 is a diagram showing a connection configuration example between a personal computer using USB and a peripheral device. The upper personal computer 100 and the hub 101 are connected by a USB cable, and the peripheral devices 102 to 105 can be connected to the lower part of the hub 101. The personal computer 100 manages the peripheral devices 102 to 105. Thus, the USB can be said to be a serial bus capable of bidirectional communication with a multi-star network structure.
[0004]
Here, the USB cable includes four signal lines. The breakdown is two for power supply and two for data signal. The data signal is basically treated as a differential signal (D ⁺ , D ⁻ ). In addition, data transfer using USB is performed by time division based on the concept that a transfer unit is a frame and stacking the frames. One frame starts with an SOF (Start Of Frame) packet. The host personal computer sequentially sends data transfer request tokens (data input requests from keyboards and cameras, and audio data output requests) scheduled in advance in the frame, so that a plurality of peripheral devices can communicate with each other. Perform data transfer in parallel.
[0005]
As technical literatures related to USB, there are, for example, “Interface” (January 1997), Japanese Patent Laid-Open No. 11-205212, and the like.
[0006]
[Problems to be solved by the invention]
By the way, in the process of USB initialization, address data is assigned to each device in order to identify the device from the host side, and identification information (for identifying the device supplier) is specified from the device side. (Hereinafter referred to as vendor ID) is transmitted to the host side, and the vendor ID is verified in the host. This vendor ID is registered and issued by an organization called UIF (USB Implemental Forum). Therefore, it has been necessary to hold the vendor ID on the device side, but a conventional holding method optimal for the device has not been sufficiently studied.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a microcomputer capable of efficiently holding identification information for specifying a supplier and smoothly performing verification of a vendor ID on a host side.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the microcomputer of the present invention includes a USB interface circuit that performs an interface for data transmission / reception between the host and the microcomputer, a nonvolatile memory for storing a program that can be electrically rewritten and read, And a CPU for executing a program read from the nonvolatile memory, wherein the nonvolatile memory has a specific memory area for storing identification information for specifying a supplier of the microcomputer. The identification information read from the specific memory area is transmitted to the host via the USB interface circuit when the USB is initialized.
[0009]
Thereby, the identification information for specifying the supplier can be efficiently held and the verification of the vendor ID on the host side can be performed smoothly.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a microcomputer according to an embodiment of the present invention.
[0011]
Hereinafter, the microcomputer 10 will be described as an 8-bit configuration. The microcomputer 10 and the personal computer 100 are connected by a pair of differential signal lines. The USB differential signals (D ⁺ , D ⁻ ) are input / output via the terminals P 1 and P 2 of the microcomputer 10. Reference numeral 20 denotes an input / output circuit connected to the terminals P1 and P2, and includes a differential input buffer 21, input buffers 22 and 23, and output buffers 24 and 25. Here, the input buffers 22 and 23 are provided in consideration of the case where the state of the USB differential signal (D ⁺ , D ⁻ ) is (L, L).
[0012]
The USB interface circuit 30 built in the microcomputer 10 is an interface for data transmission / reception with the personal computer 100. In particular, when receiving data, the USB differential signal (D ⁺ , D ⁻⁾ from the input / output circuit 20 is provided. ) To process various data. The USB differential signals (D ⁺ , D ⁻ ) are serial data signals according to the USB communication protocol.
[0013]
The USB interface circuit 30 extracts necessary data from the serial data signal. At this time, the USB interface circuit 30 determines what transfer format the serial data signal has and performs error signal processing and the like. The USB interface circuit 30 converts the serial signal subjected to the above data processing into a parallel signal (for example, an 8-bit configuration) in a predetermined format that can be processed by the microcomputer 100.
[0014]
Further, the USB interface circuit 30 includes a temporary register 31 and a control register (not shown) for temporarily storing parallel-converted 8-bit × 4 = 32-bit program data.
[0015]
Various data to be managed as a host by the personal computer 100 is set in the control register. For example, address data assigned to a device is set during USB initialization by enumeration.
[0016]
The USB interface circuit 30 performs data processing (conversion from parallel data to serial data, etc.) completely opposite to the above when data is transmitted from the microcomputer 10 to the personal computer 100.
[0017]
The RAM 40 is used for temporarily storing 32-bit unit program data sequentially transferred from the data in the temporary register 31 of the USB interface circuit 30. In order to transfer data between the USB interface circuit 30 and the RAM 40, 32 dedicated signal lines are provided. When the program data stored in the RAM 40 reaches a predetermined amount (for example, 128 bytes), the 128-byte program data is transferred to the flash ROM 50 via the bus 45 of the microcomputer 10.
[0018]
Conversely, the program data written in the flash ROM 50 can be transferred to the RAM 40, and the program data stored in the RAM 40 can be transferred to the temporary register 31 of the USB interface circuit 30.
[0019]
In general, since a large amount of data is sent from the personal computer 100 to the device side according to USB communication, a special data buffer is provided on the device side.
[0020]
On the other hand, in the present invention, the data memory is effectively utilized by adopting a configuration in which the RAM 40 that the microcomputer 10 originally has as a data memory is used for temporarily storing data by USB communication. Is also a feature.
[0021]
FIG. 2 is a block diagram showing the RAM 40 and peripheral circuits. The USB interface circuit 30 outputs an address signal ADR1, and the CPU 70 outputs an address signal ADR2, which is input to an address selection circuit 80. The address selection circuit 80 selects one of the address signals ADR1 and ADR2 and inputs it to the address designation circuit 81.
[0022]
The output of the address designating circuit 81 is input to the address decoder 41 so that the same data area can be accessed according to one of the address signals ADR1 and ADR2.
[0023]
According to the configuration described above, the data area 42 of the RAM 40 can be used as a data memory area controlled by the CPU 70 when the address signal ADR2 is selected, and the USB interface circuit when the address signal ADR1 is selected. It can also be used as a data memory area for temporarily storing program data from 30 (32-bit units). That is, the data area of the RAM 40 can be accessed from both the CPU 70 and the USB interface circuit 30.
[0024]
However, the address selection is configured to select the address signal ADR1 from the USB interface circuit 30 during data transmission / reception with the personal computer 100. This is based on the USB characteristic that data transfer from the personal computer 100 cannot be interrupted. Specifically, the microcomputer 10 is automatically set to a wait (standby) state based on a signal for detecting that the temporary register 31 of the USB interface circuit 30 is full.
[0025]
In FIG. 1, reference numeral 50 denotes a flash ROM, in which a USB control program (USB initialization program and program data write control program) is written in advance and stored from the first program area 53 and the personal computer 100. The program data is divided into a second program area 52 in which the program data is written via the RAM 40.
[0026]
A vendor ID data area 54 is provided adjacent to the first program area 53. The vendor ID data area 54 includes identification information for specifying the supplier of the microcomputer. The vendor ID data area 54 may be provided in any address area as long as it is in the flash ROM, but the address must be specified.
[0027]
Reference numeral 60 denotes a program counter whose output is applied to the address decoder 51 of the flash ROM 50. As will be described later, the output value of the program counter 60 jumps to a predetermined address according to a command from the CPU according to the state of USB communication.
[0028]
That is, when program data is written in the personal computer 100, the program counter 60 jumps to the address (FF00) which is the first address of the first program area 53 (write control program), and after the program data is written, Jump to address (0000), which is the start address of program area 52 of No. 2. Then, the CPU 70 executes the operation of the microcomputer 10 in accordance with the program instruction read from the flash ROM 50.
[0029]
Next, an example of the operation of the microcomputer 10 will be described with reference to the flowchart of FIG. First, in the first step 200, the microcomputer 10 is connected to a USB cable. At this time, the microcomputer 10 is reset by a power-on reset by turning on the microcomputer 10 through the power line of the USB cable.
[0030]
Next, in step 201, the value of the program counter 60 jumps to the address (FF00) which is the start address of the first program area 53 (write control program). Accordingly, the microcomputer 10 thereafter executes the following processing according to the write control program.
[0031]
When the microcomputer 10 is connected to the USB cable in step 201 as described above, the USB differential signals (D ⁺ , D ⁻ ) are (L, L) via the pull-up resistors provided on the microcomputer 10 side. ) To, for example, (H, L). The personal computer 100 detects that the microcomputer 100 is connected to the USB network based on the change of the USB differential signal (D ⁺ , D ⁻ ), and issues a USB bus reset signal after a predetermined time. In step 202, this USB bus reset signal is awaited.
[0032]
Step 203 is a step of determining whether or not a USB bus reset signal has been received. If NO is determined, the waiting state is maintained. If YES is determined, the process proceeds to the next step 204.
[0033]
In step 204, the USB is initialized by enumeration. Here, enumeration is a series of software processes for setting an environment in which USB data can generally be transmitted and received between the microcomputer 10 and the personal computer 100.
[0034]
The main processing performed by enumeration is initialization of the personal computer 100, processing for assigning addresses to devices controlled by the personal computer 100, and verification of vendor IDs. In the verification of the vendor ID (step 204A), the vendor ID is read from the vendor ID data area 54 of the flash ROM 50 and transmitted to the personal computer 100 via the USB interface circuit 30. On the personal computer 100 side, it is verified whether or not the vendor ID is properly registered.
[0035]
The microcomputer 10 stores a specific address assigned by the personal computer 100 in a control register (address register) in the USB interface circuit 30. As a result, the microcomputer 10 collates the address in the USB packet transmitted from the personal computer 100 after the USB initialization with the address in the address register, and is transmitted only when they match. Process USB data.
[0036]
When the environment setting capable of transmitting / receiving USB data is completed in this way, in step 205, program data to be written to the flash ROM is input from the personal computer 100 in the form of USB differential signal data (D ⁺ , D ⁻ ). Come.
[0037]
In step 206, the input USB differential signal data (D ⁺ , D ⁻ ) is processed by the USB interface circuit 30. The contents of this data processing are as described above, but the main processing is to convert serial data (8 bits × 4) into predetermined parallel data (32 bits).
[0038]
In step 207, the parallel-converted program data is written from the USB interface circuit 30 to the RAM 40. When the amount of program data written to the RAM 40 reaches a predetermined amount (for example, 128 bytes), writing is started from the RAM 40 to the second program area 52 of the flash ROM 50 via the bus 45 in units of the predetermined amount. (Step 208). This is because the flash ROM 50 is divided into a plurality of blocks, and 128 bytes are configured as a block. Therefore, the amount of data stored in the RAM 40 can be appropriately selected according to the block configuration of the flash ROM 50.
[0039]
Here, since the writing operation of the program data converted in parallel from the USB interface circuit 30 to the RAM 40 and the writing operation from the RAM 40 to the flash ROM 50 are actually performed in parallel, high-speed writing is realized.
[0040]
In step 208, writing to the flash ROM is started, but this takes a predetermined time. Therefore, in step 209, the microcomputer 10 is set to the NACK state by software. This is a kind of USB packet handshake packet, and is returned to the personal computer 100 to inform that the data from the personal computer 100 as a host cannot be accepted.
[0041]
In step 210, it is determined whether or not the writing is finished. If the determination result is NO, the NACK state is maintained. If the determination result is YES, it is set to the ACK state, and ACK is returned to the personal computer 100 to inform that the microcomputer 10 can accept data.
[0042]
In the next step 212, it is determined whether or not all program data has been written to the flash ROM 50. If the determination result is NO, the process returns to step 204 to continue writing the remaining program data. Here, since the program data is written in units of blocks (pages) (for example, 128 bytes), this process is repeated until all pages are written.
[0043]
If the determination result is YES, the value of the program counter 60 jumps to the address (0000) that is the start address of the second program area 52.
[0044]
Then, the microcomputer 10 reads the program data supplied from the personal computer 10, and the CPU 70 starts executing the operation of the microcomputer based on the decoded program command.
[0045]
In the above-described embodiment, the case where the program data is written from the personal computer 100 to the flash ROM 50 of the microcomputer 10 has been described. However, the program data written in the flash ROM 50 is read and sent back to the personal computer 100 for verification. It is also possible to perform. In that case, the order of data processing is the reverse of that described above.
[0046]
That is, the program data read from the flash ROM 50 is temporarily stored in the RAM 40 and then sequentially transferred to the USB interface circuit 30. Then, the USB interface circuit 30 performs data processing opposite to that at the time of writing, converts the parallel data into predetermined serial data, and then sends the data to the personal computer 100 via the USB cable.
[0047]
In the above-described embodiment, the first program area to which program data is to be written is empty in the initial state. However, the present invention is not limited to this, and program rewriting accompanying program upgrade can be applied in the same manner. it can.
[0048]
【Effect of the invention】
According to the present invention, a specific memory area for storing identification information (vendor ID) for specifying the supplier of the microcomputer is provided in the nonvolatile memory built in the microcomputer, and the USB is initialized. Since the identification information read from the memory area is transmitted to the host, the identification information can be efficiently held and the identification information can be collated smoothly on the host side.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a microcomputer according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a RAM and peripheral circuits of the microcomputer according to the embodiment of the present invention.
FIG. 3 is a flowchart showing an operation example of the microcomputer 10 according to the embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of a connection configuration between a personal computer using USB and a peripheral device.
[Explanation of symbols]
10 Microcomputer 20 Input / output circuit 30 USB interface circuit 40 RAM
45 Bus 50 Flash ROM
51 Address decoder 52 Second program area 53 First program area 60 Program counter 70 CPU

Claims (2)

USB for data transmission / reception interface between host and microcomputer
An interface circuit, an electrically rewritable and readable non-volatile memory for storing the program, a program counter indicating the address of the non-volatile memory, and a program read from the non-volatile memory indicated by the program counter A microcomputer comprising a CPU,
The nonvolatile memory includes a first program area in which a write control program is stored, a second program area in which program data is written by the write control program, and identification information for specifying a supplier of the microcomputer And a third program area in which is stored,
At the time of initialization, the identification information is transmitted to the host via the USB interface circuit, and the host collates the identification information, and if the identification information matches a pre-registered identification information, the host Is transmitted to the USB interface circuit, and the CPU writes the program data transmitted to the USB interface circuit to the second program area according to the write control program written to the first program area. A microcomputer characterized in that the value of the counter is set to the value of the start address of the second program area .   The microcomputer according to claim 1, wherein the host is a personal computer.

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