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Download JW-51CM User`s Manual Version 1.0
Transcript
Chapter 7: Computer Link Function [7] An example using the ring buffer (1) Data flow direction (from PC to the host computer) · Direct assignment · Ring buffer 01 Size and address: Occupy 1 K-bytes starting at 29000 · Ring buffer information storage area: Starts at 09000 Ë Parameter settings Parameter address Set value 1410, 1411 004000(8) 00 1412 01(H) 1413 0C(H) 1414 00 1415 04 1416 80(H) 1417 Details File 004000 09000 File 0 Data flow direction File 006000 29000 File 0 1 K-bytes Direct assignment Ë Processing ladder program 1 Initialize the pointers The read and write pointers should be initialized (set to 0) using a ladder program when starting the JW-51CM. 2 Write data to a ring buffer If there is free space in the ring buffer, write data in it. In this example, we assume that the data is written starting at 49000, and set the number of bytes to write in locations 09100 and 09101. 3 Update the WP After transmitting the data, the JW-51CM updates the WP. 7 There are two ways to transmit data, as shown below: Data Ring buffer 49000 Data 29000 49000 Ring buffer 29000 + WP after update + RP + WP before update + RP + WP after update 59777 39777 (a) Normal case 59777 + WP before update 39777 (b) Write to the end of the buffer and return to the top 7·48
