Users` Manual
Contents
1. Select MUX iacth Soe Address Read A D atc gt D Read Digital ecoder__ Write Digital gt Write DAC 4 16 bit 16 RWDUART Dier Address Bus Data Bus Front connector Controller A00 A15 D00 D23 Backplane Fig 4 5 Block diagram of the utility board 4 4 Utility board Updated May 12 1994 pattern approximates a pyramid 9 Test A D inputs Connect an adjustable power supply to several AIN pins in turn and examine U8 pin 20 the A D with a scope As the power supply is adjusted one of the positions in the ramp will change too Vary AIN5 C32 over the range of 1 5 to 1 5 volts while the MUX should vary over 3 to 3 volts Do this for AIN6 7 as well if desired after rejumpering the inputs Inputs AIN8 15 should be connected to a variable voltage source as the A D input is examined for unity gain 10 Board temperature Cool the temperature sensor U5 a little with a localizeable coolant and watch the first ramp position change a little 11 Constant current source Pin A27 should have close to 12 volts on it with no load 50 microamps should flow through it when connected to a load This can be checked by looking for a 1 0 volt drop accross a 20k resistor Theory of Operation The utility board provides a miscellany of support functions that are not directly involved with the readout of the CCDs These include exposure timing CCD temperature control and system voltage and temperature monitoring Bas2. Digital inputs from 0 to 15 These are read every millisecond and stored in the DSP data memory space They have resistors to pull them high if not connected Digital outputs from 0 to 15 These are written from DSP data memory every millisecond They are pulled up so they will be high until set by the DSP Two pins and for an asynchronous serial link generated by a 2681 chip The two inputs are optically isolated from the board Two pins and for an asynchronous serial link generated by a 2681 chip An input signal that will reset the DSP if brought low An open collector output signal generated by this board Low means open shutter A constant current source for CCD temperature control See Fig 4 3 4 12 Utility board Updated May 12 1994
3. eel ele eTe 1 ROM memory the watchdog timer and the source of the 15 volt power for the l 3 board Fig 4 2 gives a close up and labeling of these jumper blocks 2 JJ JJ JJ 7 3 A 5 k The analog input jumpers allow the user to configure the connection between the three analog inputs AIN5 7 and the op amps that are connected to the 16 channel A14 Write Enable MUX that goes to the A D converter Inverting non inverting and differential inputs can be configured The gain and offset ranges of the amplifiers can also be Gh ile customized with the gain resistors R5 and R7 in the AINS stage and the offset JP9 JP10 resistors R8 and R9 AIN5 is set up to read a temperature sensing diode mounted near a cooled CCD AINS is connected to the user interface connector pin C32 and ROM Configuration Jumpers Watchdog Timer Jumper oe is wired for a default non inverting gain of x2 A typical diode will exhibit a voltage JP11 S nalen drop that ranges from 0 4 to 1 0 volts from room temperature to CCD operating 2 temperatures of below 100 degrees C With a gain of x2 the output of this stage will Power Source Jumpers range from 0 8 to 2 0 volts which will be sampled by the A D converter whose input 2 si 2 A voltage range is 3 to 3 volts The diode used for laboratory test gave a reading of jee Sper A50 ADU 2640 decimal at room T to C60 ADU 3168 decimal for a cooled CCD at 127 degrees C These ADUs are mea
4. X COM_TBL to COM_TBL 15 and Y 0000 to Y 00FF The EEPROM memory map is shown in Fig 4 4 and the source code files utilboot asm and utilappl asm can be referred to for further clarification Currently an application program for testing the utility board is supplied contained in the file utiltest asm and is assigned application number 1 Application number zero is a special case and is designated for large application programs that cannot execute in their entirety from internal DSP P memory space Instructions located at EEPROM address P 200 up to P 1EEO will be executed directly from EEPROM Instructions from P APL_ADR to P 1FF will be read from EEPROM into DSP P memory by the LDA 0 command Its EEPROM memory map is also shown in Fig 4 4 The PAL U31 has been designed into the current hardware revision 3B to generate DSP reset and interrupts more reliably than earlier versions The PAL has been programmed to reset the DSP to operating mode 2 wherein the DSP begins execution from EEPROM address C000 after reset rather than reading the program from byte wide memory into DSP and then executing it as is done in operating mode 1 Earlier revisions of the DSP software than Rev 2 25 can be executed on the current hardware revision 3B but a different PAL will need to be generated to reset the DSP to operating mode 1 instead The jumper JP11 is installed in the default configuration as shown in Fig 4 2 to enable the watchdog timer It c
5. at once The exception to this is that during CCD readout the timing board cannot send any commands to the utility board Commands already received by the command buffer will be executed normally None of these application commands requires an argument and all of them generate a DON reply after they execute The following table is maintained starting in Y memory space Y 0 DIG_IN 16 bit digital word input to the board Y 1 DIG_OUT 16 bit digital word output from the board Y 2 5 DAC Four analog voltages output by the board Y 6 NUM_AD Number of A D inputs to be monitored Default is 16 Y 7 22 AD_IN Sixteen analog voltages input Y 7 Board temperature Y 8 High voltage nominally 36 volts power supply voltage Y 9 Positive low voltage nominally 15 volts power supply voltage Y 10 Negative low voltage nominally 15 volts power supply voltage Y 11 5 volts power supply voltage Y 2 DACO CCD Heater voltage output Y 12 A_CCDT Actual CCD temperature diode voltage Y 28 T_CCDT Desired CCD temperature Y 29 T_COEFF Proportionality constant for temperature control algorithmn Y 23 EL_TIM Elapsed time since start of exposure in milliseconds Y 24 TGT_TIM Target or desired exposure time in milliseconds In addition there are two X memory words that control and monitor board and software status Additional bits are defined but are of interest only to the software not the user 4 9 Utility board Updated May 12 1994 X 0 STATUS Board stat
6. initiated when the timer counts to zero This is to handle situations when the timer counts and readout is not to 4 Introduce power OFF command POF It simply resets the power control board Pin OMAN NNMN BP WN Fe WWWNN NNN NNN ND PM BM BR BF FF Re ee Ne OOWMAANI DAN BPWNHR DO ANIA UN PwWNFK O ROW a VSB DOUT7 DOUT6 DOUTS5 DOUT4 DOUT3 DOUT2 DOUTI1 DOUTO DOUT15 DOUT14 DOUT13 DOUT12 DOUTI11 DOUT10 DOUT9 DOUTS8 GND SEROUT SEROUT NC EXRESW GND AOUT3 AOUT2 GND CONST CURR AIN14 AIN12 AIN10 AIN8 AIN6 J ZZZZZZZZZZO vouuvovccovcCs o Z J 999e99s9e99899e999998999e999999999 8 odg g Z J N C N C N C ROW c VSB DIN7 DIN6 DIN5 DIN4 DIN3 DIN2 DIN1 DINO DIN15 DIN14 DIN13 DIN12 DIN11 DIN10 DIN9 DIN8 GND SERIN SERIN NC SHUTTER GND AOUTI AOUTO GND AIN15 AIN13 AIN11 AIN9 AIN7 AIN5 15 volts power supply pins from form CCD User connector as an alternative to the backplane connector JP7 and JP8 need to be set properly to utilize it Utility board Updated May 12 1994 AIN AOUT DIN DOUT SERIN SEROUT EXRES W SHUTTER CONST CURR Analog inputs 5 15 The input range of 5 7 is described on page 4 1 and the remaining ones all have an input range of 3 to 3 volts Analog output 0 4 AINO 1 are high current unipolar outputs for driving heaters from 0 to 10 volts while AIN2 3 are low current bipolar outputs of 5 to 5 volts
7. of the 16 inputs 5 of a multiplexer that is connected to a 12 bit A D converter The digital count is inversely proportional to temperature A target temperature is entered at location Y 1C 28 and the difference between it and the actual temperature located at Y 0C 12 is multiplied by a constant located at Y 1D 29 to add to the current value of the heater voltage To start up the temperature controller a reasonable value is written to the target temperature location Y 1C 28 as the default value of FFF will disable the heater The temperature controller can be disabled by writing a value of FFF to the desired temperature location since the heater will quickly be turned off since the target temperature is so much lower than the actual temperature The default value of the proportionality constant is 010000 which is appropriate to our laboratory test system that tightly couples the dewar cooling to the CCD This will probably need to be tuned by users to reflect the thermal time constant of their cooling systems with values as small as 001000 being appropriate for slower more thermally efficient systems The heater voltage time history should be monitored at the user interface connector pin C25 or by monitoring the digital counts at Y 2 written to the heater DACO to determine if it is behaving properly If the heater voltage oscillates from zero to maximum heat without damping itself out after a few minutes then the constant will have to be made s
8. that ranges from 0 to 10 volts rather than the conventional positive voltage in order to load the 12 and 12 supplies more equally The CCD can be conveniently heated with a resistor mounted near it but care should be taken to prevent the on board power transistors Q2 or Q3 from dissipating more than 1 6 watts so they don t overheat and damage the circuit board This can be easily implemented by installing a heater resistor of 35 ohms or larger which will provide a maxi mum heater power of 2 8 watts Rev 2 10 and later DSP software require 32k x 8 EEPROMs To run Rev 2 10 or later software three 28C256 EEPROMs need to be installed in the ROM sockets U13 U19 and U20 and a jumper needs to be installed on JP9 to connect the DSP address line A14 to the EEPROM which for 8k x 8 devices can be left open so a pull up resistor keeps it high Hardware memory protection is provided by JP10 the EEPROMs can only be written to if a jumper is installed To summarize U13 U19 and U20 JP9 Install jumper to use 32k x 8 EEPROMs DOO D23 JP10 Install jumper to write enable the EEPROMs T Aet ee BOOTROM X mem BOOTROM P mem 6200 6100 6000 Fig 4 4 shows the EEPROM memory map The boot program utilboot asm Notussd starts execution at location 6000 which is accessed when the DSP reads from i 4000 location E000 since A15 is not wired from the DSP to the EEPROM after it is reset into operating mode 2 This is different from the VM
9. E and timing boards that have only one byte wide EEPROM and reset into the special DSP56001 boot APPL 2 P mem _ 2300 i APPL 1 Y mem operating mode 1 that reads the boot program into the DSP a byte at a time The APPL 1 X mem A boot program has communication and command recognition software and is APPL 1 P mem 2000 APPL 0 Y mem loaded into the DSP internal memory locations P 0000 to APL_ADR B0 for APPL O Komen eee Rev 2 25 and X 0000 00FF Code for several commands is located starting 4 RIEGO at address P OVL_ADR 6200 for Rev 2 25 and are called overlay programs because they re similar to the timing and VME board commands although they APPLICATION 0 are a bit different on the utility board in executing directly from EEPROM Fe program memo hang without having to be written to the DSP internal memory The application ick 0000 program can be loaded into the DSP with the LDA command from EEPROM 20 44 EEPROM memory map or alternatively downloaded from the host computer by repeated calls to the WRM command The LDA command takes a single argument which is the number of the application program to be read from EEPROM and is between 0 and 10 Application programs 1 to 10 are located in the EEPROM starting at 4 2 Utility board Updated May 12 1994 address 2000 and are allocated 300 words per program They are read into the internal DSP memory spaces P APL_ADR to 1FF
10. Reset A reset circuit on the board is implemented with the PAL programmable array logic chip U31 to reset the DSP and generate interrupts to it from a variety of signal sources The PAL equation is as follows RESETI QRES UTLRST UTLRSW IRQA RESETI amp MSCK IRQB RESET PULSE7 amp IIRQB where means logical OR amp means logical AND and means logical invert The DSP reset line RESETI will go low is asserted when either the watchdog timer line QRES goes high the power control board brings the UTLRST line low from the system backplane the on board reset switch is depressed or the EXRESW pin on the user connector is grounded the later two causing UTLRSW to go low The DSP interrupt line IRQA goes low if the DSP reset line RESETT is asserted or if the millisecond interrupt line MSCK goes low The IRQA line is sampled along with IRQB when RESETI is asserted to determine the operating mode of the DSP which determines its internal memory configuration IRQB goes high if the DSP reset line goes low so the DSP is placed in operating mode 2 on reset which starts the DSP executing code read starting at external memory address E000 which is mapped to the EEPROMs IRQB is asserted as an interrupt when either PULSE7 or IIRQB goes low PULSE7 is generated by the timing board allowing it to interrupt the utility board at will and the IIRQB is bussed along the backplane allowing external devices to interrupt the utility bo
11. UTILITY BOARD This chapter has been updated to describe circuit board Revision 3B dated 3 30 93 and the current revision of the DSP software 2 30 Hardware Preparation Fig 4 1 shows the placement of the major components of the utility board The board contains a DSP provision for up to 32k x 24 bit external program memory regulators for 12 volt power two high current drivers for heaters four digital to analog converters DACs an analog to digital A D converter with a 16 input multiplexer 16 digital inputs and 16 digital outputs three configurable analog input amplifiers a Analog Input Jumpers oy m yo z z S Serial I O iii temp Backpl D00 DO8 D16 ackplane nets Do7 D15 D23 Connector Analog Input U13 U19 U20 Resistors A D f Vi bors U31 PAL DADS JP9 L JP10 ROM Power Transistors Regulators Prodam ROMS Jumpers spt User Interface Connector 12V 12V Reset Switch pap l Rev 3B U34 Power Source Jumpers 74F07 L GND I J Fig 4 1 Component layout of Utility board manual reset switch and two 96 pin DIN connectors Jumper blocks are located in Analog inpot Jupes four areas and control the configuration of the analog input amplifiers the program
12. ard as well As of Rev 2 25 neither of these interrupt sources are connected to anything and interrupt service routine is not written to support IRQB so it exists for future system enhancements 12 System Reset An optically isolated line is provided on the front plane connector that can be used to reset the utility board from a remote location in the event of a catastrophic failure 13 Additional serial communications Two additional bidirectional asynchronous serial ports are provided One is optically isolated and wired to the front plane connector for use with terminals or external computer systems and may be particularly useful for debugging The second one is connected to the backplane for communicating with other devices that may be installed by the user on the backplane These are provided by the serial controller U25 which is not currently being populated on distributed utility boards nor is it supported by DSP software Users desiring this support should contact us Software Commands The DSP software chapter details the commands that are located in the utilboot asm program that is loaded from EEPROM soon after the DSP is reset and are in common with the other DSP boards in the system The file utilappl asm contains the main exposure control power on interrupt servicing and temperature control software It is the designated application number 0 that can be executed directly from EEPROM and is loaded with the 7LDA 0 command I
13. ard is being used Alternatively the daisy chained lines A21 A22 and B04 need to have jumpers attached to them on the VMEbus backplane to connect them between the utility board and the power control board Board Checkout The following procedure is followed in verifying operation of the board The commands to be executed are described later in this chapter 1 Visually inspect board The correct ROM s should be installed if there is only one ROM it should be in the left most socket Check the DSP The jumpers described above should be installed correctly as should all the resistors 2 Power supplies The 5 should be available at the logic devices and 12 volts should be available at the regulators and the analog components With the power control board installed and the utility board installed in either slot 1 or 6 PON will turn on the analog voltages If it doesn t install jumpers on the power control lines 4 3 Utility board Updated May 12 1994 to enable the power supplies Spot check the voltages 3 Stand alone DSP test U31 pin 1 PAL should show a 1 millisecond period square wave after the LDA command has been executed low for 1 5 of its duty cycle U8 pin 18 the A D should have a low going pulse of 120 nanosec duration every one millisecond the interrupt time 4 ROM boot Monitor pin 20 on any of the ROMs It should toggle for approx 400 microsec after either the reset button is depressed or digital power is turne
14. d VME interface boards 9 EEPROM support A bank of fast EEPROM memory is supplied with each board that contains the boot code in compiled from the source file utilboot asm This bank is fairly large 32k x 24 bits enabling large programs to be executed by the utility board and timing board programs to be downloaded over the serial link connecting the two boards The time critical portion of the DSP program operates out of internal DSP memory at 10 MIPS whereas non time critical portions operates more slowly out of the EEPROM because the DSP requires extra clock cycles for an external memory access EEPROM programming support is described in the software chapter The memory read and write commands RDM and WRM operate transparently on either DSP or EEPROM memory depending on the specified address A time of 10 milliseconds for any write to EEPROM is required for each word and page mode writes are not supported 10 Watchdog timer It monitors the execution of the on board DSP processor and one of the outputs of the timing board If it detects that either board is not alive an error message will be sent to the host computer If the utility board DSP is not alive the DSP will be reset whereas the timing board will be reset or 4 7 Utility board Updated May 12 1994 not depending on the setting of a control bit Resetting the DSP will cause the current exposure to be lost and corrective action must be taken by the host computer 11 Board
15. d on After the 400 microsec it should stay in the high state and the DSP will begin normal operation A storage scope is needed for this 5 Test Data Link The data link to the timing board should be checked Execute the DSP command TDL from the host computer one million times There should be no errors 6 Test DACs Execute the DSP command TDA Examine the outputs of the four DACs with a scope They should ramp linearly from about 0 to 9 volts with rounded bottoms pins C24 and C25 and from 5 to 5 volts A24 and A25 7 Test A D Jumper pins A25 to C30 Execute the DSP command TAD Monitor A24 and A25 with the scope A25 should show a ramp and A24 should show a somewhat different ramp with a small discontinuity when A25 crosses zero volts 8 Test MUX With the DSP in a free running interrupt driven state the board may need to be reset examine U8 pin 20 the A D and U31 pin 1 the PAL with a scope triggering on the latter The former is the output of the MUX and should show 12 step changes as the various inputs are connected to the MUX The envelope 2 Front connector 20 MHz clock DUART Counter External Reset il 1 millisec clock ET Port A IRQA a Asynchronous Serial Link SCI RXD TXD i Reset Status and control lines Timer Port B lt g Power Board Temp lt PortA Port A lt gt DSP56001 12 bit ie OPUS S A D MUX 12 bi 11 EEPROM ee ed S o a z DAC _ 32k x 24 4 16 bit 16
16. e SEX command one from the utility board soon after the command is issued and the second from the VME interface board when the readout has completed 5 Power Supply monitoring and control Four of the inputs to the 16 input multiplexer are connected to the power supply lines that are bussed on the backplane 5 15 15 and 36 volts They are sampled every millisecond and placed in a table in DSP memory which can be accessed anytime by the host computer with a RDM command Additionally a power up routine successively turns on each analog power supply with a digital on off line from the backplane after the timing board has successfully loaded all its DACs This function has been developed and is part of Rev 2 25 software and is to be used in systems equipped with a power control board Power turn on is initiated with the PON command The sequence is as follows 1 The utility board boots up from on board ROM 2 The host computer should issue a LDA to the timing board and LDA and PON commands to the utility board PON is the command to start the power on sequence 3 The utility board will reset the power control board by asserting PWRST to initialize its on board counters and turn off the power supply switches 4 The utility board issues an IDLE command to the timing board to ensure that its clock driver DACs 4 6 Utility board Updated May 12 1994 are properly loaded with legal values 5 The utility board instructs t
17. ed around a Motorola DSP56001 microprocessor the utility board can be programmed by the user to support other functions such as an additional temperature controller dewar level and ID shutter status LED drivers for status indication and switch monitoring for direct system control without a host computer A interrupt circuit forces the DSP to update all inputs and outputs every millisecond providing precise exposure timing while 12 bit A D and D A converters offer good analog precision Commands are received from the timing board over a fast serial link and processed as necessary Additional serial links can be used to communi cate with other devices A block diagram of the board is shown in Fig 4 5 The following utility board functions are available 1 Command and Interrupt processing The boot routine utilboot asm loaded from EEPROM to internal DSP memory soon after DSP reset provides communications service through the serial link to the backplane services external commands It follows the protocol discussed in the systems manual of processing and generating header ID words that contain three bytes source byte a destination byte and a number of words byte The commands TDL RDM WRM LDA and RST are implemented in the same fashion on all the DSP boards 2 CCD temperature monitor and control An amplifier circuit U1b measures the voltage drop on a temperature sensing diode located near the CCD The amplifier output is connected to one
18. he power control board to turn on the low voltage power lines nominally 15V by toggling the LVEN line 128 times These will be ramped up over a 20 millisecond time period 6 The utility board samples the low voltage power lines making sure they are within tolerance If not an ERR message is sent to the host computer If yes processing continues 7 The utility board turns on the high voltage supply nominally 36 volts by toggling the HVEN line 128 times It checks it to be within range after 5 milliseconds If yes a DON message is sent to the host computer to indicate that power has been succesfully turned on Otherwise an ERR message is sent If the power control board fails to turn on successfully the host computer can be used to examine the voltages seen by the utility board during the power on sequence The target voltages HV 36 LV 15 and LV 15 the required tolerances the actual voltage measured during the power on sequence and the current voltage values are all stored in Y memory on the utility board in the following locations Target Tolerance Power on Current HV 36 Y 1F Y 20 Y 25 Y 8 LV 15 Y 21 Y 22 Y 26 Y 9 LV 15 Y 23 Y 24 Y 27 Y A 6 Digital and Analog I O Every millisecond an interrupt service is entered that reads the voltages at each of the sixteen digital inputs and sixteen analog inputs and stores them in a table in the DSP memory They can be read at any time by the host proce
19. maller Similarly if the heater seems to take a long time to settle to the correct value as it oscillates by a small amount from its average then it can be sped up by entering a larger proportion ality constant 3 Board temperature monitoring A temperature monitor is placed directly on the utility board and connected to one of the sixteen inputs to the multiplexer allowing the host computer to read the 4 5 Utility board Updated May 12 1994 board temperature at any time The gain calibration is 0 38 degrees C per ADU 4 Exposure timing Exposure timing is controlled by counting millisecond interrupts It begins counting from zero at the start of an exposure up to a target exposure time Counting can be paused at any time while the exposure time can be changed by setting a different exposure time which if less than the elapsed exposure time will cause an immediate readout Upon reaching the target exposure time the utility board will close the shutter if needed and signal to the timing board via a serial line that readout should begin The target exposure and elapsed times are readable by the host computer at any time and their addresses are listed below The shutter can be controlled with the utility board with bit 0 of the software control word at X 1 being set indicating that the shutter is to be opened at the beginning of the exposure and closed when it terminates The command SEX starts an exposure initiates the exposure timer and s
20. ontains a timer circuit that will reset the DSP unless the watchdog timer is itself reset more often than that The intention is to require the DSP to reset the watchdog timer more often than every 10 milliseconds as a sign that it is properly functioning otherwise the DSP will be reset The timer circuit is reset with a simple read instruc tion from location FFF7 The two jumpers JP7 and JP8 supply power to the board from either the backplane or the CCD User connector The default is to supply 15 volt power from the backplane to the utility board Some users may desire to supply it through the CCD User connector instead so the utility board can independently verify the integrity of the backplane power supply before turning it on and powering up the CCDs In that case the two jumpers on JP7 8 should be moved to the 2 3 position the separate power should be run to the CCD User connector through pins C01 15 V and A01 15 V and a sample of the backplane power before it is supplied to the backplane should be run to several of the inputs AIN8 15 after being suitably divided so they are in the range of 3 to 3 volts that the A D requires Note that the spacing of the pins of JP7 8 are larger than 0 10 inches so standard jumpers cannot be installed the intention of having soldered wires is to discourage accidental re configurations The utility board needs to be installed in either slot 1 or slot 6 of the VME system backplane if a power control bo
21. ssor with a RDM command to the appropriate address given below A table of sixteen digital outputs plus shutter and four analog outputs is also maintained in DSP memory and written to latches every millisecond as well Whenever the host computer needs to change any of these values it writes new values into the correct DSP memory location with the WRM command after which the DSP will update the latches on the next interrupt cycle after a delay of at most one millisecond The analog to digital converter is 12 bits in accuracy and presents 2 s complement codes to the DSP program that converts it to straight binary with 0000 representing 3 volts and OFFF representing 3 volts input to the A D converter 7 Software downloading Capability for downloading software from the host computer to the utility board DSP is done with the WRM command provided on all DSPs DSP software compiled on the host computer is sent over the fiber optic link to the timing board which relays it to the DSP on the utility board There it is written to the DSP internal memory for direct execution 8 Serial communications An asynchronous serial connection between the utility and timing boards is provided It is connected to the SCI Serial Communications Interface port of both DSPs operates at 312 5 kbits second and is serviced by interrupt service routines at each end It is the only communications channel between the utility board and the timing an
22. sured by the host computer examining Fig 4 2 Jumper blocks Y 12 with the RDM command This gives a relation between ADUs and temperature 4 Utility board Updated May 12 1994 ane yee retiree T deg C 773 0 2841 x ADU Constanteurrent A7 Users should calibrate their systems with the temperature sensing diodes ended AE ae then have installed in their dewars using the above calibration as an initial and A D s estimate Details of the temperature control algorithm are discussed below Yy The two remaining inputs AIN6 7 are shipped with identical input resistors to the AINS stage but the jumpers are wired for a grounded input so the output to the MUX connected to the A D is at zero volts The user can easily EE change to a non inverting x2 gain or an inverter with a simple jumper AOTP See lt change The user should refer to the circuit schematic when configuring Heater 86 ohms minimum gt resistor alternative input configurations Fig 4 3 Connection for CCD temperature control A constant current source supplying 50 microamps is provided on pin A27 and should be connected as shown in Fig 4 3 for use with temperature sensing diodes near the CCD Two resistors R1 and R2 are connected in parallel to the constant current source FET Q1 These are trimmed to provide 50 microamps to within one percent so the temperature calibration will be the same for different utility boards The CCD heater power is provided as a voltage
23. t interprets the following commands SEX Start exposure Immediately begin a timed exposure by issuing a CLR command to the timing board waiting for it to terminate opening the shutter if the shutter status bit is set beginning the timer countdown according to the exposure time word stored in Y data memory and issuing commands to the timing and VME interface board to begin readout PEX Pause exposure Simply close the shutter stop the timer and wait until a REX command is issued REX Resume exposure Open the shutter if needed and resume the normal exposure sequence 4 8 Utility board Updated May 12 1994 AEX Abort exposure Immediately stop exposing altogether by closing the shutter put the CCD in idle mode and put the VME interface board in command interpreting mode OSH Open shutter Open the shutter Normally this will be done by the SEX command but this command is provided as a manual override for testing and special purposes CSH Close shutter Close the shutter SYR System reset Reset the timing board by pulling the backplane SYSRST signal low PON Power on Turn analog power on safely using the power control board POF Power Off Turn off the analog power using the power control board Commands may be sent in groups to be executed by the DSP as it gets to them There is a circular buffer for commands in the DSP that is 32 words long so fairly lengthy sequences of commands may be sent
24. tarts readout It is a fairly integrated command that is defined in the utilappl asm file as follows 1 Utility board receives and recognizes SEX command 2 Utility board issues CLR command to timing board to clear the CCD and waits for it to reply with a DON when this is complete 3 If X OPTIONS 1 bit OPT_SH 0 equals 1 then open the shutter The shutter can either be connect ed to the utility board preferred or the timing board older systems 4 The elaspsed time at Y 23 is zeroed and the status bit X STATUST_EX bit OPT_EX 1 is set to indicate that an exposure is in progress so the elapsed time will be incremented by 1 each millisecond interrupt 5 The utility board sends a DON reply to the host computer to indicate that the exposure has been started 6 Once the elapsed time equals the target time readout is initiated by the utility board The shutter is closed if needed A RDC command is issued by the utility board to both the timing and the VME interface boards 7 The timing board begins readout and transfers pixel data to the VME interface board 8 The VME interface board interprets all data coming from the timing board as pixel data and places them in the image areas specified until the specified number of pixels have been transferred after which it issues a DON command to the host computer and switches to normal command interpreting mode Note that the host computer receives two DON replies after issuing th
25. us word BitO ADC Set it A Ds and temperature control needs updating Bit1 Timer Set if a timed exposure is in progress Bit2 Shutter Set if shutter is open Xl SOFTWARE CONTROL BitO Shutter Set if shutter is to be opened when exposure starts Other bit assignments will be added as we go along following this general structure All these words are serviced every one millisecond as signalled by the external interrupt generation circuitry The file utiltest asm is assigned application number 1 and contains several simple routines written to test the functionality of the utility board These commands should NOT be executed with the utility board user connec tor plugged into a CCD system The section above describing the board checkout procedure should be referred to for further details concerning system interconnection when executing these commands TDA Test Digital to Analog converters This will generate ramping numbers that are written to the four DACs so their outputs can be examined with an oscilloscope TAD Test Analog to Digital converter This will generate a ramp for a DAC that is wired by the user to one of the analog MUX inputs for conversion by the A D converter Its digitized output is then written to a second DAC whose analog output is examined by a scope and compared to the first DAC s output TDG Test Digital Test the digital input and output circuits by reading the 16 inputs and outputting them to each digital outp
26. ut in turn right shifting the 16 bit data word The CCD User connector is a 96 pin female connector mounted near the reset switch Its pinout is given below which the pinout for the system backplane connector is given in the system chapter above Software revision history Several changes were made to the following files in the transition from Rev 2 25 to 2 30 utilboot asm The SCI receiver ISR was compressed considerably It is the same ISR as timboot asm except register R2 points to the SCI address not RO utilappl asm 1 The OSHUT and CSHUT routines no longer send messages to the timing board to open or close the shutter We now assume that the shutter is connected to this board 2 The interrupt structure was changes considerably to minimize the code in interrupt service routines so registers and stacks are not altered while processing an interrupt Specifically the TIMER ISR only counts down the timer and closes the shutter setting the ST_READ bit it readout is to occur which is now in a program routine with the bit checked at the START location The SERVICE soubroutine was introduced to service the millisecond interrupts and does all the A D DAC digital 4 10 Utility board Updated May 12 1994 I O and temperature control servicing occur and to separate the readout functions from the timer ISR servicing Pinout CCD User conector VSB 3 Anew STATUS bit ST_READ was introduced to indicate that readout is to be
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