GE Medical Systems Information Technologies 340MT WMTS Transmitter User Manual Description

GE Medical Systems Information Technologies Inc. WMTS Transmitter Description

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1Serial Protocol for the STn00 and SRn00 devicesIssue 2Date 5/6/001IntroductionThis document describes the serial protocol for re-programming the STn00and SRn00 range of transmitter and receiver modules.There is an important difference between the VHF and the UHF productswhich concerns the Intermediate Frequency (IF) used.To differentiate between the ST and SR each has a unique product code. For the SRn00 this is 0F6 hex and for STn00 it is 0F5 hex.2Data FormatTwo baud rates are used for differing functions. Throughout this document,which one is being used is given. The two baud rates are:Baud rate 19,200, 8 data bits, 1 start bit, 1 stop bit, no parityBaud rate 1,200, 8 data bits, 1 start bit, 1 stop bit, no parityThe internal PIC is running an RC clock which can vary considerable withcomponent tolerance and temperature. To overcome this, a serial protocol isused which looks a the input waveform from the PC as a pulse, the durationof which determines whether the input data is a binary 1 or 0. If the baud rateis 19,200, the data byte to be transmitted to the radio is as follows:0 (decimal) =binary 0255 (decimal) =binary 1During readback the data can vary and so must be interpreted as follows: Value < 241 (dec) = binary 0Value $ 241 (dec) = binary 1For the one data byte, 8 bytes must be sent representing each bit.If the baud rate is 1,200, then the data sent is a normal 8 bit byte.Note: throughout the document the value of the data is given assuming anRS232 interface. If TTL or similar logic levels are used then the datamust be inverted.
23DefinitionsThe following give details of the terms used thoughout this document.3.1 FoscThis is the value of the Reference Oscillator in the radio. This is NOTprogrammable and the value is not stored in EEPROM. Currently there aretwo types used by the ST/SRn00 units:12.8 and 14.85 MHz.3.2 FcFc is the Comparison Frequency used by the synthesizer in the radio. This isa programmable parameter, but care should be taken if it is changed,because the synthesiser hardware is optimized for certain values of Fc. TheFc in use with the ST/SRn00 family vary for the different applications, but isone of these discrete values:5, 6.25, 10, 12.5 ,20 or 25 KHz (refer to Wood & Douglas for the actual values allowed).Fc is not directly stored as a number in the radio’s EEPROM. It is ratherindirectly stored as the “Rvalue” (see below).3.3 RvalueThis number is the result of the division:Rvalue = Fosc / FcSince the ST/SRn00 family can have one of two Fosc: 12.8 or 14.85 MHz, thepossible Rvalues for the radio are:If Fosc= 12.8MHz:RR1(5) =2560 (dec), A00 (hex)RR1(6.25) =2048 (dec), 800 (hex)RR1(10) =1280 (dec), 500 (hex)RR1(12.5) =1024 (dec), 400 (hex)RR1(20) =640 (dec), 280 (hex)RR1(25) =512 (dec), 200 (hex)
3If Fosc= 14.85MHz:RR2(5) =2970 (dec), B9A (hex)RR2(6.25) =2376 (dec), 948 (hex)RR2(10) =1485 (dec), 5CD (hex)RR2(12.5) =1188 (dec), 4A4 (hex)RR2(20) =NOT possible (result is not integer no.)RR2(25) =594 (dec), 252 (hex)From above it is clear that we have 11 possible values for the combination of2 Fosc and 6 Fc’s. When the Rvalue is read from the unit the current Fc and Fosc. can be determined from these values.Note: Rvalue is stored as 2 bytes in EEPROM locations 61, 623.4 IFIF is the Intermediate Frequency of the receiver. Its value for the STn00family is always zero, but for the SRn00 family is as follows:SRn00 with frequency range < 200 MHz:, “High Side” (+45 MHz)SRn00 with frequency range > 200 MHz, “Low Side” (- 45 MHz).STn00, any frequency IF = 0Note: The IF value is not stored in the unit’s EEPROM. The type of ST or SRn00 must be known before programming can be carried out.4Channel Information and StorageFor both the ST and SRn00 family, 16 random and 112 sequential channelscan be stored in the non-volatile EEPROM memory area of the internal PICprocessor. Channels 0 - 15 are stored individually in the EEPROM andchannels 16 - 127 are calculated from the start frequency and the table stepincrement.In principle frequency is stored in a two byte format plus the high byte offset. The data stored is not the frequency itself, but the frequency divided by theFc. In other words if the desired frequency for the random channel N isFreq(N), then the value stored is F(N) where F(N) is calculated as:F(N) = [Freq(N) + IF] / FcThe result is stored as:EEPROM(60) = int [F(N)/65536] *256 high byte offsetEEPROM(N) = int [F(N)/256] - EEPROM(60) msbEEPROM(N + 16) = F(N)- [EEPROM(60) + EEPROM(N)] *256 lsb
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5Or if a read-back is performed, the frequency on channel N is calculated as:Freq(N) = {{{[ EEPROM(60)+ EEPROM(N)]*256 }+ EEPROM(N+16)} - IDF }*Fc Hzwhere IDF = IF/FcSimilarly, for the Sequential table start, if desired frequency is FreqS, then:FS = [FreqS + IF] / Fcand the result is stored as:EEPROM(56) = int[FS/65536] *256 high byte offsetEEPROM(57) = int[FS/256] - Eeprom(56) msbEEPROM(58) = FS- [EEPROM(56) + Eeprom(57)] *256 lsbThe sequential table step is stored in location 57 as a multiple of FcThe sequential table is limited by the value stored in location 51 (0-111), butit can not exceed 111. If the value is > 111 then limit should be imposed asfollows:MaxCh = EEPROM(51) Sequential ch. LimitIf MaxCh > 111 thenMaxCh = 111 Limit MaxCh Number to 111 !endifIf read-back is performed, the Start of the Sequential table is calculated as:SeqFreqStart = {{{[ EEPROM(56)+ EEPROM(57)]*256 }+ EEPROM(58)}- IDF }*Fcwhere IDF = IF/Fc this is Intermediate Frequency as a multiple of FcAnd a sequential table step is:SeqFreqStep = EEPROM(59)*Fc [Hz]
65EEPROM locationsThe PIC processor used in the STn00 and SRn00 units has an area of non-volatile memory EEPROM area. The contents of this data is given in the following table:Location Description0 - 15 RX/TX div msbs16 - 31 RX/TX div lsbs32 - 47 not used48 - 49 reserved50 not used51 is sequential table limit channel (0-111)52 - 53 reserved54 SETUP flags byte (default is FF). At the moment only relevant flag is one occupying bit no 1 and it isSerial or Parallel mode of operation. In Serial Mode Channel selectedis the one defined in loc. 63 of EEPROM and is written using PC andserial interface. In parallel mode the switch in the unit (D0 to D2lines) defines channel selected by the unit. In parallel mode only ch.0 to 7 are accessible.55 reserved56 high byte offset for sequential table 57 sequential table start hi byte58 sequential table start lo byte59 sequential table step increment60 high byte offset 61 Rvalue hi byte62 Rvalue lo byte63 serial channel selectedNote: RESERVED locations are planned for future useNOT USED locations are not used with no plans for future use.
76Command TypesThere are 3 types of packet to be sent to the radio from the PC:Short packetLong packetDirect packetThese are described in the following sections.6.1 Short packetThis is used to send out single instruction to the radio to carry out functionslike setting serial or parallel mode of operation, setting the serial channelnumber etc.For the short packet the 8 data bytes to be transmitted are:Xproduct ID. For the SRn00 = 0F6 hex and for STn00 = 0F5 hexAEEPROM address or DATA1BEEPROM data byte or DATA2Cnot used (0) or DATA3Dnot used (0) or DATA4COM command byte chkH check sum hi byte } A + B + C + D + COMchkL check sum lo byte }Note: This data is sent out at 19200 baud as detailed in section 2. Eachdata byte within the packet should be separated by 10 to 15 msec.delay and the delay between 2 successive packets should be > 100msec.The Command (COM) byte is defined as follows:6.1.1 COM # 63 decThis denotes a long packet as described in section 6.2 for re-programmingthe EEPROM area.6.1.2 COM = 64 decThis is the direct packet mode as described in section 6.3 and is used tochange the channel of the unit.
86.1.3 COM = 66 decThis invokes the EEPROM read-back mode. After this command and apacket, the radio will respond with a reading back of the whole content of theEEPROM (64 bytes), one after another, without any address bytes etc.The data returned from the radio is at 19,200 as defined in section 2 of thisdocument.6.1.4 COM = 67 decThis invokes the single byte programming of the EEPROM where:AEEPROM address BEEPROM dataThis is used to change the mode of operation (Serial / Parallel) or for thesetting of the serial channel number.As an example, to set the parallel mode of operation only, the followingpacket must be sent:Xchr(0F6) hex for SRn00 or chr(0F5) hex for STn00AEEPROM address byte chr(54 dec)BEEPROM data byte chr(255) for parallelCnot used (0)Dnot used (0)COM chr(67) decchkH chr(1) }chkL chr(120 dec) } for parallel mode (total check sum 376 dec.)For setting the serial channel, two packets must be sent. First the shortpacket must be sent with B data = 253, followed by the Direct packet asshown in section 6.3.6.1.5 COM = 70 decThis resets the radio and should be sent at the end of the Long packet afterthe EEPROM contents have been re-programmed.
96.2 Long PacketThe Long packet mode is intended to re-write the entire EEPROM area of theunit (64 locations). The format is similar to the short packet with a fewdifferences as shown below:XProduct ID. For the SRn00 = 0F6 hex and for STn00 = 0F5 hexAEEPROM DATA1 (from addr COM + 0)BEEEPROM DATA2 (from addr. COM +1)CEEPROM DATA3 (from addr. COM +2)DEEPROM DATA4 (from addr. COM +3)COM command byte = EEPROM address of the first data byte in ablock chkH check sum hi byte }A + B + C + D + COMchkL check sum lo byte }16 packets like above are expected once started, covering all 64 EEPROMlocations.Note: This data is sent out at 19200 baud as detailed in section 2. Thereshould be > 15 msec delay between bytes and > 100 msec. in betweenpackets.A short packet (with COM = 70) should be sent at the end of the Long packetto reset the device.6.3 Direct PacketCurrently there is only one “Direct packet” in use and it is intended for thechannel number change.. This 3 byte packet is sent at 1,200 baud asdetailed in section 2. The form of the data packet is as follows:chr(64 dec)chr(Channel Number)chr(149 dec)

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