Host computer wants to write byte 0x55 at address 0x1543 to the device with address 0x08 (Note that read/write bit is cleared in the answer). Device memory contains 0xAA at this address. Host computer wants to read byte at address 0x345 from the device with address 0x02. Data format in this protocol allows one to access a number of devices making use the same continuous address space with 3-byte address.ġ. Usually read or write access to the device memory using this protocol takes not more than 2ms for every byte at 115.2 Kbit/s. Baudrate could be selected from 9.6, 19.2, 57.6 or 115.2 Kbit/s by dip switch inside the device (Table 2). This requires all word (16-bit integer) and float variables to be swapped in the IBM compatible PC, that use big endian byte order.Ĭommunication parameters are always 8-bit with 1 stop bit, no parity, no flow control. Byte ordering is little endian, high byte has low address. The only thing user should know about it is controller memory map, which is of course different for every device, and device address. Once implemented, such a protocol could be used with any device of this type. This protocol makes it possible to represent any serial device as a array of bytes with transparent access to process variables. If it is not correct XOR-sum, packet is ignored. If bit 6 = 1, packet contains special command.īits 5÷0 – high bits of 14-bits address field. Bit 7 = 1 corresponds to write command and bit 7 = 0 – read command.īit 6 – special command flag.
Two most significant bits are ignored.īit 7 – read/write bit. Should be equal to device address set on the dip switch inside the device or packet will be ignored otherwise. The device sends 5-byte answer for every 5-byte command, if device address field and XOR-sum in this command is correct.Ħ-bit device address. Protocol is based on 5-byte binary packets exchange (See Table below). It could contain also some special commands which are described separately for every device. Cooling system for Lambda wheels silicon detectorĬommunication protocol for all our devices consists of two main commands: read memory byte and write memory byte.Time Expansion Chamber / Transition Radiation Detector.CELGAS – Nuclear Polarisation in Molecular Hydrogen.CHUPS – Circulating Hydrogen Ultrahigh Purification System.PolFusion – polarized dd-fusion experiment.
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