JPH032950A - Reception buffer control system - Google Patents

Abstract

PURPOSE:To prevent a process carried out at the reception side from progressing up to an unfixed part of the data stored in a reception buffer in a simple constitution by providing a means which shows the boundary position between the readable and unreadable parts of the written reception data. CONSTITUTION:A pointer RF is provided for control of a reception buffer 10 and points a boundary between a part which may possibly be cancelled with detection of an error and a part which has no such possibility within the buffer 10. The control is carried out so that the reading operation of the buffer 10 does not exceed the pointer RF. Thus it is possible to invalidate the reception data block while minimizing the complication of constitution for the transfer of data carried out via the buffer 10.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a reception buffer management method in a data reception device.

[Prior art and its problems] In data receiving devices such as printers, received data is processed within the device, so in most cases this data is sequentially stored in a receive buffer of an appropriate size and read out sequentially starting from the oldest data. We will process it. To manage such sequential storage and reading, write pointers and read pointers are used, respectively.

If you try to apply a method to the buffer management described above, in which data is transferred in the middle of a block, and if an error is detected in a block, the entire block is deleted from the receive buffer and the entire block is retransmitted, the following will occur. A problem arises. That is, a block is generally found to have an error only after the beginning of the block or the entire block has been written to the receive buffer. If the internal processing of the device is progressing quickly, there is a possibility that reading from the receive buffer has already progressed into the current block by the time it is determined that there is an error in this block.

[Purpose of the invention]

The present invention solves the problems of the prior art described above, and provides a receive buffer management method that makes it possible to invalidate received data blocks while minimizing the complexity of the configuration in data transfer using a receive buffer. The purpose is to

[Summary of the invention]

According to an embodiment of the present invention, in order to manage the receive buffer, a boundary between a portion of the receive buffer that may be canceled due to detection of an error, etc., and a portion that is not likely to be canceled is specified. Provide a pointer controlled by

The above objective is achieved by controlling the reading from the receive buffer so that it does not proceed beyond this pointer.

[Embodiments of the invention]

An embodiment of the present invention will be described above based on the drawings. In this embodiment, data transfer from the host to the receiving device is performed according to the following protocol.

■Data transfer from the host to the receiving device is performed in blocks.

■Every time the host finishes sending one block of data, it gives a status confirmation command to the receiving device.

(2) If there is an error in the block of data received immediately before, the receiving device deletes the block from the reception buffer in response to the status confirmation command, and notifies the host of the error status. The host that is notified of the error status retransmits the block.

■If there is no error, the receiving device responds to the status confirmation command to the effect that it is normal. In this case, the host is able to transfer the next block and also process the successfully received block in the receive buffer.

FIG. 1 is a diagram showing the initial state of a receiving buffer to which an embodiment of the present invention is applied. In the figure, WP is a write pointer, R? is a read pointer, and RF is a read fence pointer to prevent the read pointer from advancing any further. In the state shown in the figure, there is no data in the reception buffer 10, so the three pointers WP, RP, and R
All F points to the same position.

FIG. 2 shows a state in which one block of data has been read into the reception buffer 10, but error checking has not yet been completed. This error check is performed using, for example, CRC, but since the error check method itself is not the gist of the present invention and is well known to those skilled in the art, further explanation will be omitted.

As can be seen from FIG. 2, in this state, the write pointer WP has advanced by one block, but the read fence pointer RF remains at the same position as in FIG. Since the read pointer RP cannot overtake the read fence pointer RF, it also remains at the same position as in FIG. 1.

FIG. 3 shows a state in which when an error is discovered by error checking, the block is deleted in response to a status confirmation command from the host side.

As can be seen from the figure, a block is deleted by moving the write pointer WP back by one block. As explained with reference to FIG. 2, the read pointer is prevented from entering a block whose error has not been confirmed, that is, the data within this block is prevented from being read. Therefore, data in blocks containing errors will not be processed.

The receiving device deletes the block and notifies the host of the error, so the host responds by retransmitting the previous block. If the reception is successful this time, the receiving device responds to the status confirmation command to notify that it is normal, and advances the read fence pointer RF.

Only at this stage is the receiving device able to process the data in the previously received block.

FIG. 4 shows a state in which reading from the receiving buffer IO by the receiving device has proceeded to a certain extent.

FIG. 7 diagrammatically shows a sequence representing the operations described above.

5 and 6 show the process when the next block of data is normally received after the state shown in FIG. 4. Note that FIG. 6 shows the state immediately after the read fence pointer RF is advanced. Here, in (A), the read pointer is the read fence pointer R just before that.
(B) shows the case where the read pointer RP has not yet caught up with the read fence pointer RF.

Note that the actual receiving buffer is realized in the form of a ring buffer or the like, but the specific method of configuring such a receiving buffer is well known to those skilled in the art, and therefore a description thereof will be omitted.

Although the above description has been made based on one embodiment, it goes without saying that the present invention is not limited to this and includes various modifications.

For example, instead of deleting a block from the receive buffer after the entire block has been placed in the receive buffer, a block may be removed from the receive buffer when it becomes clear that the currently received block is no longer needed (e.g. due to detection of a parity error). may be done immediately).

Additionally, blocks can be deleted without waiting for status confirmation from the host side.

Further, in the embodiment, deletion of a block due to error detection has been described, but the scope of application of the present invention is not limited to this. Applicable in certain cases. For example, it can be applied to cases in which it is determined whether or not to perform some processing on received data, or to discard it as unnecessary data even though it is not an error.

Furthermore, it goes without saying that the present invention can be applied to protocols other than those described above.

〔Effect of the invention〕

As explained above, according to the present invention, with a simple configuration,
It is possible to prevent processing on the receiving side from proceeding to an undefined portion of data in the receiving buffer.

[Brief explanation of drawings]

1 to 6 are diagrams for explaining the operation of an embodiment of the present invention, and FIG. 7 is a diagram for schematically explaining the operation sequence shown in FIGS. 1 to 6. IO = Receive buffer WP: Write pointer RP: Read pointer RF: Read fence pointer Figure 1 Figure 2

Claims (2)

[Claims] (1) A receiving buffer in which received data is sequentially written and sequentially read out is provided with means for indicating a boundary position between a portion of the written received data that may be read and a portion that is not allowed to be read. Receive buffer management method. (2) A first pointer indicating the end position of the received data, a second pointer indicating the position where the reading was last performed, and a third pointer serving as means for indicating the boundary position. 2. The reception buffer management system according to claim 1, wherein reading based on the second pointer is configured not to exceed the boundary indicated by the third pointer.