Differences
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usp:usp_spec [2012/12/04 19:31] – admin | usp:usp_spec [2015/04/16 16:27] (current) – external edit 127.0.0.1 | ||
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===== Terminology ===== | ===== Terminology ===== | ||
- | * Master - the device issuing commands. Master is running USP client software. Master is identified by | + | * Master - the device issuing commands. Master is running USP client software. Master is identified by ModuleID = 0. |
* Slave - the device listening for USP commands. Slave is running USP server software. | * Slave - the device listening for USP commands. Slave is running USP server software. | ||
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^ Checksum Word (required) | ^ Checksum Word (required) | ||
- | *A command consists of two or more 32-bit words. The first 32-bit word is divided into 4 fields. The highest 8 bits (bits 31-24) identify the command. The next 16 bits (bits 23-8) is the Unit ID or Address. The next 8 bits specify the number of 32 bit words in the command including the first and last word. | + | *A command consists of two or more 32-bit words. The first 32-bit word is divided into 4 fields. The highest 8 bits (bits 31-24) identify the command. The next 16 bits (bits 23-8) is the ModuleID-Hi and ModuleID-Lo. The next 8 bits specify the number of 32 bit words in the command including the first and last word. |
*The command word is followed by optional 1 – N data words. The interpretation of data depends on command. | *The command word is followed by optional 1 – N data words. The interpretation of data depends on command. | ||
*The last word contains 3 bytes of data (bits 21-16) and simple additive checksum (bits 7-0). | *The last word contains 3 bytes of data (bits 21-16) and simple additive checksum (bits 7-0). | ||
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When the slave device needs to signal that it has a status change it may send break signal to the master device. The signal is one 32 bit word, it comprises break character command ID (0x55) and USP Slave module ID. | When the slave device needs to signal that it has a status change it may send break signal to the master device. The signal is one 32 bit word, it comprises break character command ID (0x55) and USP Slave module ID. | ||
- | Master will recoginze break by checking that CommandID == 0x55 and the Lenght | + | Master will recoginze break by checking that CommandID == 0x55 and the Length |
**Command** | **Command** |