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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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AM79761 датащи(PDF) 10 Page - Advanced Micro Devices |
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AM79761 датащи(HTML) 10 Page - Advanced Micro Devices |
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10 / 20 page  10 Am79761 PRELIMINARY Word Alignment The Am79761 device provides 7-bit comma character recognition and data word alignment. Word synchroni- zation is enabled by asserting EN_CDET HIGH. When synchronization is enabled, the Am79761 device con- stantly examines the serial data for the presence of the Comma character. This pattern is 0011111XXX, where the leading zero corresponds to the first bit received. The comma sequence is not contained in any normal 8B/10B coded data character or pair of adjacent char- acters. It occurs only within special characters, known as K28.1, K28.5, and K28.7, which are defined specifi- cally for synchronization purposes. Improper alignment of the comma character is defined as any of the follow- ing conditions: 1. The comma is not aligned within the 10-bit trans- mission character such that TXD0...TXD6 = “0011111.” 2. The comma straddles the boundary between two 10-bit transmission characters. 3. The comma is properly aligned but occurs in the re- ceived character presented during the rising edge of RCLK rather than RCLKN. When EN_CDET is HIGH and an improperly aligned comma is encountered, the internal data is shifted in such a manner that the comma character is aligned properly in RXD[0:9]. This results in proper character and half-word alignment. When the parallel data alignment changes in response to an improperly aligned comma pattern, some data which would have been presented on the parallel output port may be lost. However, the synchronization character and subsequent data will be output correctly and properly aligned. When EN_CDET is LOW, the current align- ment of the serial data is maintained indefinitely, regardless of data pattern. When encountering a comma character, COM_DET is driven HIGH to inform the user that realignment of the parallel data field may have occurred. The COM_DET pulse is presented simultaneously with the comma char- acter and has a duration equal to the data, or half of an RCLK period. The COM_DET signal is timed such that it can be captured by the adjoining protocol logic on the rising edge of RCLKN. Functional waveforms for synchronization are given in Figure 18 and Figure 19. Figure 18 shows the case when a comma character is detected and no phase adjustment is necessary. It illus- trates the position of the COM_DET pulse in relation to the comma character on RXD[0:9]. Figure 19 shows the case where K28.5 is detected, but it is out of phase and a change in the output data alignment is required. Note that up to three characters prior to the comma character may be corrupted by the realignment process. Figure 18. Detection of a Properly Aligned Comma Character RCLK RCLKN COM_DET RXD[0:9] K28.5 TChar TChar TChar 21560A-4 Note : TChar = 10-bit Transmission Character |
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