KR20020001262A - Memory management of endpoints in USB device - Google Patents

Abstract

PURPOSE: A method for managing memories of end points within a USB device is provided to improve data transmission efficiency of the USB device. CONSTITUTION: A USB(Universal Serial Bus) includes a device communicating with a host. A memory area is embedded in the device for storing data during communication with the host. End points receive assignment of the whole memory area and are connected with the host for receiving data from the host or transmitting data to the host. Each end point shares the memory area and reports the size of memory of each end point as the size of the memory area to the host. In case of receiving data from the host, the rest end points except end points being used in data receiving generate NAK signals to out token signals of sending data from the host, so that data receiving is delayed. In case of transmitting data to the host, flag bit is generated from the memory area connected to end points being used in data transmission. The end points are divided into receiving-only end points receiving data from the host and transmitting-only end points transmitting data to the host.

Description

Memory management of endpoints in USB devices

The present invention relates to a device control method, and more particularly, to a memory management method of endpoints in a USB device.

Universal Serial Bus (USB) is an industry-defined interface for connecting peripherals to the system bus of personal computers. USB features a 1: 1 interface with various peripherals, including mice, keyboards, monitors, printers, mass storage drivers, modems, faxes, and more. This reduces manufacturing costs and makes it easier for personal computer users to configure their systems.

USB is a token-based bus architecture. The USB host broadcasts the tokens on the bus, and the USB device matching the address contained in the token transfers data to or accepts data from the host.

A USB device can provide a number of channels used for communication with a host, and as a general term in the USB specification, these channels are referred to as "pipes." Each pipe connects a host with endpoints in the device, so that the device receives data from the host at the endpoints, writes data to the endpoints, and sends the data to the host. In other words, each pipe can transmit data bidirectionally. In case of data communication between the host and the device, when the host receives the number and size of endpoints in each device during initialization, if the data needs to be transmitted larger than the size of the reported endpoint, the large data is converted into the size of the endpoint. Cut and send in multiple packets.

Endpoints in existing USB devices have their respective memory areas in accordance with the USB specification. There are cases where a memory applied to each endpoint uses a FIFO composed of flip-flops (F / F) and a memory cell composed of registers. The use of FIFOs has the advantage that the logic for controlling flip-flops (F / F) is reduced and the size of the memory is fixed, whereas in the case of using memory cells, the memory of the memory can be set by selectively setting registers. You can change the size. 1A and 1B illustrate memory management of these endpoints.

That is, as shown in FIG. 1A, the endpoints EP0, EP1,... , EPn, x bytes, y bytes,… , z bytes, respectively, indicating that endpoints configured as flip-flops (F / F) have a finite memory size. In Fig. 1B, the respective endpoints EP0, EP1,... Where EPn includes a portion specifying a start address and a memory size, n bytes, and n are divided by the start address and the memory size to correspond to the corresponding endpoints, respectively. Is set to be. This means that the memory size of the endpoint is set according to the memory size assigned to the endpoint, indicating that the memory size of the endpoint is variable.

However, both cases report the number and size of endpoints in each device to the host when initiating data transfer between the host and the device. Thus, although the size of the endpoint set before the data transfer is an endpoint consisting of a variable register, the amount of data to be transferred is determined only by the size of the reported endpoint. In other words, when data larger than the size of an endpoint is transmitted, data must be divided and transmitted. As a result, a phenomenon in which data transmission efficiency is lowered occurs.

Therefore, there is a need for a method that can transfer a large amount of data at once when transferring data to a USB device. Of course, it is possible to transmit a lot of data by increasing the size of the endpoint, but this implies an inefficient problem in hardware configuration.

It is an object of the present invention to provide a memory configuration method of an endpoint that can improve the data transfer efficiency of a USB device.

In order to more fully understand the drawings used in the detailed description of the invention, a brief description of each drawing is provided.

1A-1B illustrate memory management of endpoints in a conventional USB device.

2 is a diagram illustrating memory management of endpoints in a USB device according to an embodiment of the present invention.

In order to achieve the above object, a memory management method of a USB endpoint of the present invention comprises a USB including a device for communicating with a host, the memory area being embedded in the device and storing data during the communication; And endpoints, wherein the entire memory area is allocated and connected with the host to transfer the data to or from the host, each of the endpoints sharing the memory area and having its memory size to the host. Is reported as the size of the memory area.

Preferably, when receiving data from the host, the other endpoints other than the endpoint used to receive the data generate a NAK signal for an out token signal to send out data from the host to receive data. In the case of delaying and transmitting data to the host, flag bits are generated in the memory area connected to the endpoint used for the data transmission to prevent writing of other data.

In addition, the endpoints are divided into dedicated reception endpoints receiving data transmitted from the host and transmission dedicated endpoints transmitting data to the host.

The USB endpoint memory management method of the present invention improves data transfer efficiency.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. For each figure, like reference numerals denote like elements.

2 is a diagram illustrating a memory configuration method of an endpoint according to an embodiment of the present invention. In Fig. 2, the endpoints EP0, EP1,... , EPn _-1 , EPn, are divided into two groups, each group dedicated to transmission or reception.

The reason for distinguishing the endpoints to be dedicated to sending and receiving separately is that when data is sent to and received from the endpoint without distinguishing between sending and receiving, a token to receive data from the host in the case of transmission is called an IN token. The data to be transmitted until it is generated is known as endpoints, EP0, EP1,... Since it should be stored at, EPn _-1 , EPn, it can not be received while waiting for transmission, which reduces the data transmission efficiency. So, the dedicated transmit endpoints, EP0, EP1,... Dedicated receive endpoints while transferring data to the host via,. The data transmission efficiency is improved by receiving data through EPn- ₁ , EPn.

These endpoints, EP0, EP1,... The memory allocated to, EPn- ₁ , EPn, respectively, is set to be the entire memory area embedded in the USB device. As shown in Fig. 2, the dedicated transmit endpoints, EP0, EP1,... , And receive dedicated endpoints,... , EPn _-1 , EPn, each consisting of n bytes of registers. Endpoints with a memory size of n bytes will report their memory size, or maximum size, to the host if the device address is allocated after a protocol reset command from the host.

In general, when transmitting data to an endpoint with a small memory size, data is divided into several packets, and each packet is transmitted with control signals irrelevant to actual data, such as a device address and a frame start signal (SOP). The error correction signal CRC, the packet number PID, the end frame signal EOP, and the like are also transmitted each time. Therefore, according to the present invention, if the data transmitted to the endpoint is smaller than the maximum size of the endpoint, the data transmission is completed at one time. The number of packets is small compared to conventional small endpoints. That is, the number of times to be transmitted in the packet is relatively small. Each time a packet is delivered, the interrupt operation of the microcontroller (MCU) associated with control signals irrelevant to the actual data is also reduced.

However, each endpoint, EP0, EP1,... Since EPn _-1 and EPn use the same memory area and n bytes, conflicts between data transmitted and received may occur. In order to prevent this, the present invention uses the following method.

First, suppose that one endpoint, for example EPn, is receiving data using n bytes of memory when the device receives data. The remaining endpoints then send a NAK signal to the token to export data from the host, i.e., the OUT token, which indicates that the microcontroller (MCU) is sent by the endpoint EPn. The reception of data is delayed until all the n bytes of used data have been read.

Next, when the device transmits data, for example when it is transmitted via endpoint EP0, a flag bit is generated if the data to be transmitted is in n bytes of memory to prevent writing of other data.

Thus, even if endpoints share memory, data can be transmitted and received without data collision.

As an example of applying the above method, it will be described that the data transmission efficiency is improved by the present invention. In transmitting 1000 bytes of data, a device's endpoint has 256 bytes of memory and consists of three CONTROL, INTERRUPT, and IN / OUT endpoints.

In this case, in the conventional method, the size of the input / output endpoint is about 64 bytes even if a small size is allocated to the remaining control and interrupt endpoints. To handle 1000 bytes of data, 16 interactions on the USB, 16 interrupts for the MCU to read the data, time for reading the data, and an out token for the host to send the next data A response to the NAK signal indicating that data cannot be received for the (OUT token) should be processed.

However, according to the present invention, when allocating 256 bytes to the endpoints, four interactions and four interrupts required to read data and NAK response while reading data are required.

This result is about 30% of data transfer efficiency considering that it is allocated out token which takes much of the time to process the data transmission, handshake time and interrupt processing in the MCU. Is improved.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The USB endpoint memory management method of the present invention described above improves data transfer efficiency.

Claims (3)

In a USB including a device to communicate with the host, A memory area embedded in the device to store data during the communication; And An endpoint having the entire memory area allocated and connected with the host to transmit the data to or from the host, Each of the endpoints sharing the memory area and reporting its memory size to the host as the size of the memory area. The method of claim 1, When receiving data from the host, the other endpoints other than the endpoint used to receive the data generate a NAK signal for the out token signal to send out data from the host to delay data reception. When transmitting data to the host, the memory management method of the USB endpoint to generate a flag bit in the memory area connected to the endpoint used for the data transmission to prevent the writing of other data. The method of claim 1, wherein the endpoints are And a dedicated dedicated endpoint for receiving data transmitted from the host and a dedicated dedicated endpoint for transmitting data to the host.