DOUBLE BUFFERED SCALER CARD ----------------------------- Most Recent Revision 2-JUN-1995 BOARD DESCRIPTION: The Double Buffered Scaler Card, DBSC, provides 4 channels of 40 bit scalers per card (Scaler Number1 through Scaler Number4). Each scaler channel has a Clock input (CLK1 through CLK4) and two Gate inputs (GATE1A, GATE1B through GATE4A, GATE4B). These inputs are all Differential ECL and can be terminated on the DBSC card with a 110 ohm resistor. If no signal is connected to a gate input then it assumes a default enabled state. The scalers can be individually Reset from the computer over the C BUS. The Reset is an Asynchronous over riding reset. There are 4 LED's for each Scaler Channel, 16 LED's total. The LED's display the State of the following signals: Clock, Gate A, Gate B, and Reset. Scaler channel Number 1 is special because the low order 32 bits may be read by a front panel LED display. The low order 32 bits of Scaler Channel Number 1 are also available from a rear panel connector (J1) as Differential ECL signals. Each scaler consists of 5 bytes of 74AS867 counters followed by 5 byte wide dual path double buffers AM29520's. The scalers can be read out over the C BUS and into the control computer. The Scalers increment on the rising (positive) edge of the Clock Input. A scaler will only increment when both of it's Gate Inputs (Gate A and Gate B) are LOW. Normally if nothing is connected to these Gate Inputs then they are held LOW by internal resistor networks. All of the Clock and Gate inputs can be terminated by 110 ohm resistor networks. The scalers use the following Timing and Synchronization Signals from the Specific Mother-Board Bus: Timing & Sync. A is used to control which section of the 29520's are written into. When Timing and Sync. Signal A is high then the A half of the 29520's is selected for writting into, and when the Timing and Sync. Signal A is low than the B half of the 29520's is selected for writing scaler data into. Timing & Sync. B is used to LATCH & SHIFT the data in the 29520's. The data is LATCH & SHIFTED on the rising positive edge of the Timing & Sync. Signal B. Timing & Sync. Signal C is used to select which section of the AM29520 is read. When Timing & Sync. Signal C is assereted then the A-half of the AM29520 is read. When the signal is negated then the B-half of the buffer is selected. Function Address bit 8 is used to select either the input-half (current beam crossing) or the output-half (previous beam crossing) of the AM29520 to be read. Function Address bit 8 High => current beam crossing information and Function Address bit 8 Low => previous beam crossing information. The Double Buffer Scaler Card may be read using the C-BUS Fast Read Cycle. PROGRAMING: ----------- The Double Buffered Scaler Card is read using the following Function Addresses: SCALER BYTE FUNCTION ADDRESS CHANNEL NUMBER NUMBER PREVIOUS CROSSING CURRENT CROSSING -------------- ------ ----------------- ---------------- 1 1 (LSB) 1 129 1 2 2 130 1 3 3 131 1 4 4 132 1 5 (MSB) 5 133 2 1 (LSB) 9 137 2 2 10 138 2 3 11 139 2 4 12 140 2 5 (MSB) 13 141 3 1 (LSB) 17 145 3 2 18 146 3 3 19 147 3 4 20 148 3 5 (MSB) 21 149 4 1 (LSB) 25 153 4 2 26 154 4 3 27 155 4 4 28 156 4 5 (MSB) 29 157 The Double Buffered Scaler Card is RESET by writing a data byte with contents 5 to the following Function Addresses: RESET SCALER FUNCTION CHANNEL NUMBER ADDRESS -------------- -------- 1 1 2 9 3 17 4 25 INPUT-OUTPUT CONNECTIONS: DOUBLE BUFFERED SCALER CARD CONNECTORS ------------------------------------------ CONNECTOR J1 SCALER NUMBER 1 OUTPUT DATA THE 32 LEAST SIGNIFICANT BITS ------------- ------------------------------------------------------------------------------ Plug & PIN Color Function Wire # Mnemonic # on cable on cable ------------------------------------------------------------------------------ 1 Ground GND 2 Ground GND 3 brown Scaler Num. 1 Output Bit#1 Non-inverted IN 1 NSC1 4 tan Scaler Num. 1 Output Bit#1 inverted IN 2 ISC1 5 red Scaler Num. 1 Output Bit#2 Non-inverted IN 3 NSC2 6 tan Scaler Num. 1 Output Bit#2 inverted IN 4 ISC2 7 orange Scaler Num. 1 Output Bit#3 Non-inverted IN 5 NSC3 8 tan Scaler Num. 1 Output Bit#3 inverted IN 6 ISC3 9 yellow Scaler Num. 1 Output Bit#4 Non-inverted IN 7 NSC4 10 tan Scaler Num. 1 Output Bit#4 inverted IN 8 ISC4 11 green Scaler Num. 1 Output Bit#5 Non-inverted IN 9 NSC5 12 tan Scaler Num. 1 Output Bit#5 inverted IN 10 ISC5 13 blue Scaler Num. 1 Output Bit#6 Non-inverted IN 11 NSC6 14 tan Scaler Num. 1 Output Bit#6 inverted IN 12 ISC6 15 violet Scaler Num. 1 Output Bit#7 Non-inverted IN 13 NSC7 16 tan Scaler Num. 1 Output Bit#7 inverted IN 14 ISC7 17 grey Scaler Num. 1 Output Bit#8 Non-inverted IN 15 NSC8 18 tan Scaler Num. 1 Output Bit#8 inverted IN 16 ISC8 19 white Scaler Num. 1 Output Bit#9 Non-inverted IN 17 NSC9 20 tan Scaler Num. 1 Output Bit#9 inverted IN 18 ISC9 21 black Scaler Num. 1 Output Bit#10 Non-inverted IN 19 NSC10 22 tan Scaler Num. 1 Output Bit#10 inverted IN 20 ISC10 23 brown Scaler Num. 1 Output Bit#11 Non-inverted IN 21 NSC11 24 tan Scaler Num. 1 Output Bit#11 inverted IN 22 ISC11 25 red Scaler Num. 1 Output Bit#12 Non-inverted IN 23 NSC12 26 tan Scaler Num. 1 Output Bit#12 inverted IN 24 ISC12 27 orange Scaler Num. 1 Output Bit#13 Non-inverted IN 25 NSC13 28 tan Scaler Num. 1 Output Bit#13 inverted IN 26 ISC13 29 yellow Scaler Num. 1 Output Bit#14 Non-inverted IN 27 NSC14 30 tan Scaler Num. 1 Output Bit#14 inverted IN 28 ISC14 31 green Scaler Num. 1 Output Bit#15 Non-inverted IN 29 NSC15 32 tan Scaler Num. 1 Output Bit#15 inverted IN 30 ISC15 33 blue Scaler Num. 1 Output Bit#16 Non-inverted IN 31 NSC16 34 tan Scaler Num. 1 Output Bit#16 inverted IN 32 ISC16 35 violet Scaler Num. 1 Output Bit#17 Non-inverted IN 33 NSC17 36 tan Scaler Num. 1 Output Bit#17 inverted IN 34 ISC17 37 grey Scaler Num. 1 Output Bit#18 Non-inverted IN 35 NSC18 38 tan Scaler Num. 1 Output Bit#18 inverted IN 36 ISC18 39 white Scaler Num. 1 Output Bit#19 Non-inverted IN 37 NSC19 40 tan Scaler Num. 1 Output Bit#19 inverted IN 38 ISC19 41 black Scaler Num. 1 Output Bit#20 Non-inverted IN 39 NSC20 42 tan Scaler Num. 1 Output Bit#20 inverted IN 40 ISC20 43 brown Scaler Num. 1 Output Bit#21 Non-inverted IN 41 NSC21 44 tan Scaler Num. 1 Output Bit#21 inverted IN 42 ISC21 45 red Scaler Num. 1 Output Bit#22 Non-inverted IN 43 NSC22 46 tan Scaler Num. 1 Output Bit#22 inverted IN 44 ISC22 47 orange Scaler Num. 1 Output Bit#23 Non-inverted IN 45 NSC23 48 tan Scaler Num. 1 Output Bit#23 inverted IN 46 ISC23 49 yellow Scaler Num. 1 Output Bit#24 Non-inverted IN 47 NSC24 50 tan Scaler Num. 1 Output Bit#24 inverted IN 48 ISC24 51 green Scaler Num. 1 Output Bit#25 Non-inverted IN 49 NSC25 52 tan Scaler Num. 1 Output Bit#25 inverted IN 50 ISC25 53 blue Scaler Num. 1 Output Bit#26 Non-inverted IN 51 NSC26 54 tan Scaler Num. 1 Output Bit#26 inverted IN 52 ISC26 55 violet Scaler Num. 1 Output Bit#27 Non-inverted IN 53 NSC27 56 tan Scaler Num. 1 Output Bit#27 inverted IN 54 ISC27 57 grey Scaler Num. 1 Output Bit#28 Non-inverted IN 55 NSC28 58 tan Scaler Num. 1 Output Bit#28 inverted IN 56 ISC28 59 white Scaler Num. 1 Output Bit#29 Non-inverted IN 57 NSC29 60 tan Scaler Num. 1 Output Bit#29 inverted IN 58 ISC29 61 black Scaler Num. 1 Output Bit#30 Non-inverted IN 59 NSC30 62 tan Scaler Num. 1 Output Bit#30 inverted IN 60 ISC30 63 brown Scaler Num. 1 Output Bit#31 Non-inverted IN 61 NSC31 64 tan Scaler Num. 1 Output Bit#31 inverted IN 62 ISC31 65 red Scaler Num. 1 Output Bit#32 Non-inverted IN 63 NSC32 66 tan Scaler Num. 1 Output Bit#32 inverted IN 64 ISC32 67 Ground GND 68 Ground GND 69 Power +5.0 V VCC 70 Power +5.0 V VCC 71 Power -5.2 V VEE 72 Power -5.2 V VEE 73 Ground GND 74 Ground GND 75 NOT USED . . . . . . 138 NOT USED 139 Ground GND 140 Ground GND CONNECTOR J2 THE SPECIFIC BACKPLANE BUS CONNECTOR ------------- ------------------------------------------------------------------------------ Plug & PIN Color Function Wire # Mnemonic # on cable on cable ------------------------------------------------------------------------------ 1 Ground GND 2 Ground GND 3 Gate A Scaler Number 1 Non-Inverted NGAS1 4 Gate A Scaler Number 1 Inverted IGAS1 5 Gate B Scaler Number 1 Non-Inverted NGBS1 6 Gate B Scaler Number 1 Inverted IGBS1 7 Clock Scaler Number 1 Non-Inverted NCLS1 8 Clock Scaler Number 1 Inverted ICLS1 9 Gate A Scaler Number 2 Non-Inverted NGAS2 10 Gate A Scaler Number 2 Inverted IGAS2 11 Gate B Scaler Number 2 Non-Inverted NGBS2 12 Gate B Scaler Number 2 Inverted IGBS2 13 Clock Scaler Number 2 Non-Inverted NCLS2 14 Clock Scaler Number 2 Inverted ICLS2 15 Gate A Scaler Number 3 Non-Inverted NGAS3 16 Gate A Scaler Number 3 Inverted IGAS3 17 Gate B Scaler Number 3 Non-Inverted NGBS3 18 Gate B Scaler Number 3 Inverted IGBS3 19 Clock Scaler Number 3 Non-Inverted NCLS3 20 Clock Scaler Number 3 Inverted ICLS3 21 Gate A Scaler Number 4 Non-Inverted NGAS4 22 Gate A Scaler Number 4 Inverted IGAS4 23 Gate B Scaler Number 4 Non-Inverted NGBS4 24 Gate B Scaler Number 4 Inverted IGBS4 25 Clock Scaler Number 4 Non-Inverted NCLS4 26 Clock Scaler Number 4 Inverted ICLS4 27 NOT USED . . . . . . 66 NOT USED 67 Ground GND 68 Ground GND 69 Power +5.0 V VCC 70 Power +5.0 V VCC 71 Power -5.2 V VEE 72 Power -5.2 V VEE 73 Ground GND 74 Ground GND 75 brown TSS-A SELECT WRITE A/B Non-inverted IN 1 NTSA 76 tan TSS-A SELECT WRITE A/B Inverted IN 2 ITSA 77 red TSS-B LATCH/SHIFT Non-inverted IN 3 NTSB 78 tan TSS-B LATCH/SHIFT Inverted IN 4 ITSB 79 orange TSS-C SELECT READ A/B Non-inverted IN 5 NTSC 80 tan TSS-C SELECT READ A/B Inverted IN 6 ITSC 81 yellow Timing & Sync. Signal D Non-inverted IN 7 NTSD 82 tan Timing & Sync. Signal D Inverted IN 8 ITSD 83 green Timing & Sync. Signal E Non-inverted IN 9 NTSE 84 tan Timing & Sync. Signal E Inverted IN 10 ITSE 85 blue Timing & Sync. Signal F Non-inverted IN 11 NTSF 86 tan Timing & Sync. Signal F Inverted IN 12 ITSF 87 violet Timing & Sync. Signal G Non-inverted IN 13 NTSG 88 tan Timing & Sync. Signal G Inverted IN 14 ITSG 89 grey TSS-H LED's OFF Non-inverted IN 15 NTSH 90 tan TSS-H LED's OFF Inverted IN 16 ITSH 91 white Card Address Bit#1 Non-inverted IN 17 NAC1 92 tan Card Address Bit#1 Inverted IN 18 IAC1 93 black Card Address Bit#2 Non-inverted IN 19 NAC2 94 tan Card Address Bit#2 Inverted IN 20 IAC2 95 brown Card Address Bit#3 Non-inverted IN 21 NAC3 96 tan Card Address Bit#3 Inverted IN 22 IAC3 97 red Card Address Bit#4 Non-inverted IN 23 NAC4 98 tan Card Address Bit#4 Inverted IN 24 IAC4 99 orange Card Address Bit#5 Non-inverted IN 25 NAC5 100 tan Card Address Bit#5 Inverted IN 26 IAC5 101 yellow Card Address Bit#6 Non-inverted IN 27 NAC6 102 tan Card Address Bit#6 Inverted IN 28 IAC6 103 green Function Address Bit#1 Non-inverted IN 29 NAF1 104 tan Function Address Bit#1 Inverted IN 30 IAF1 105 blue Function Address Bit#2 Non-inverted IN 31 NAF2 106 tan Function Address Bit#2 Inverted IN 32 IAF2 107 violet Function Address Bit#3 Non-inverted IN 33 NAF3 108 tan Function Address Bit#3 Inverted IN 34 IAF3 109 grey Function Address Bit#4 Non-inverted IN 35 NAF4 110 tan Function Address Bit#4 Inverted IN 36 IAF4 111 white Function Address Bit#5 Non-inverted IN 37 NAF5 112 tan Function Address Bit#5 Inverted IN 38 IAF5 113 black Function Address Bit#6 Non-inverted IN 39 NAF6 114 tan Function Address Bit#6 Inverted IN 40 IAF6 115 brown Function Address Bit#7 Non-inverted IN 41 NAF7 116 tan Function Address Bit#7 Inverted IN 42 IAF7 117 red Function Address Bit#8 Non-inverted IN 43 NAF8 118 tan Function Address Bit#8 Inverted IN 44 IAF8 119 orange Strobe Non-inverted IN 45 NSTB 120 tan Strobe Inverted IN 46 ISTB 121 yellow Direction Non-inverted IN 47 NDIR 122 tan Direction Inverted IN 48 IDIR 123 green Bidirectional Data Bit#1 Non-inverted IN 49 NDB1 124 tan Bidirectional Data Bit#1 Inverted IN 50 IDB1 125 blue Bidirectional Data Bit#2 Non-inverted IN 51 NDB2 126 tan Bidirectional Data Bit#2 Inverted IN 52 IDB2 127 violet Bidirectional Data Bit#3 Non-inverted IN 53 NDB3 128 tan Bidirectional Data Bit#3 Inverted IN 54 IDB3 129 grey Bidirectional Data Bit#4 Non-inverted IN 55 NDB4 130 tan Bidirectional Data Bit#4 Inverted IN 56 IDB4 131 white Bidirectional Data Bit#5 Non-inverted IN 57 NDB5 132 tan Bidirectional Data Bit#5 Inverted IN 58 IDB5 133 black Bidirectional Data Bit#6 Non-inverted IN 59 NDB6 134 tan Bidirectional Data Bit#6 Inverted IN 60 IDB6 135 brown Bidirectional Data Bit#7 Non-inverted IN 61 NDB7 136 tan Bidirectional Data Bit#7 Inverted IN 62 IDB7 137 red Bidirectional Data Bit#8 Non-inverted IN 63 NDB8 138 tan Bidirectional Data Bit#8 Inverted IN 64 IDB8 139 Ground GND 140 Ground GND SWITCH U85 CARDS ADDRESS SELECTOR SWITCH This switch controls the Card Address at which this card will wake up. When a switch is closed the coresponding bit in the Card Address is a 0 and when a switch is open then the corresponding bit is a 1. ADDRESS SWITCH SECTION CARD ADDRESS BIT BIT VALUE ---------------- ------------------ ----------- 1 6 32 2 5 16 3 4 8 4 3 4 5 2 2 6 1 1 7 ALWAYS CLOSED 8 ALWAYS CLOSED BOARD ORDERS HISTORY: 8 BOARDS ORDERED NOV 1986 ETCH REVISION HISTORY: REVISION A DEC 1986 ECO HISTORY: none POWER REQUIREMENTS: The DBSC uses VCC (+5V), VEE (-5.2V) and GROUND power supply connections. The calculated power consumption is: VCC: typical maximum ------- ------- 74x and 29520 chips: 5.4 A 8.1 A 10KH chips: N/A 0.8 A LED's 0.3 A 0.7 A ------- ------- 6.5 A 9.6 A VEE: maximum ------- 10KH chips: 1.3 A VEE pulldown 0.1 A VTT pulldown 0.7 A (power comes from VEE supply) ------- 2.1 A PARTS LIST: QUANTITY ITEM -------- ------ 1 74 AS 04 1 74 AS 08 1 74 ALS 32 5 74 ALS 138 2 74 ALS 520 7 74 ALS 540 9 74 ALS 541 20 74 AS 867 11 10 H 124 10 10 H 125 3 10 H 188 20 AM29520 2 7902 54 LED 1 8 POSITION DIP SWITCH 16 56 OHM 8 PIN SIP 7 330 OHM 8 PIN SIP 3 470 OHM 8 PIN SIP 4 4700 OHM 8 PIN SIP 12 110 OHM 1/4 WATT RESISTORS 6 330 OHM 1/4 WATT RESISTORS 2 140 pin connectors right angle SPECIAL USAGE AND MODIFICATIONS TO REVISION A: ------------------------------------------------------ Input Connections for Use in the FSTD Cell ------------------------------------------ The Double Buffered Scaler Cards used for Specific Trigger Fired and Enable count require two modifications: 1. All CLK inputs on the back of the card must be tied together. This is accomplished using the termination resistor mounting holes. Clips are to be put in those holes to hold wire-wrap wire. Then connect all of the non-inverting inputs together, and do the same for the inverting inputs. 2. Gate A1 through Gate A4 must have 110 Ohm termination resistors mounted near the back of the card. 11-AUG-1988 Hardware RESET of Scaler Number 1 on a DBSC Card ------------------------------------------------ Scaler number 1 on the DBSC card can be setup to use and external differential ECL line for a hardware Reset of the scaler count. This can be accomplished using the following steps. 1. Disconnect the GATE B Scaler #1 line that runs from U69 pin 5 to U10 pin 23 and U11 pin 11. The trace to cut is on the Solder Side. The LED driver is left connected to U69 pin 5. 2. Ground the remaining U10 pin 23, U11 pin 11 net using a via near U11. 3. Disconnect the Clear Scaler #1 bar line (Clear Scl1 Bar) line that runs from U90 pin 11 to U14 pins 1 and 2. A good trace to cut is on the solder side. Leave U90 connected to the LED driver. 4. Connect U69 pin 5 to U10 pins 1 and 2. This is the hardware reset signal. Now the Scaler #1 Gate B input is an external Reset for Scaler #1. Diff ECL Low --> Reset Diff ECL High --> Do Not Force Reset 25-APRIL-1992 Combine Scaler #1 and Scaler #2 Outputs to Make the TAS Number -------------------------------------------------------------- The TAS Number is made by combining the lowest 4 bits of Scaler #1 with the first 12 bits of Scaler #2. This is accomplished by disconnecting some of the LED Driver Output Driver circuits from Scaler #1 and connecting them to Scaler Number 2. 1. Cut 12 of the connections from the output of Scaler #1 to the Led Driver Output Driver circuits. These traces are cut on the component side of the card. The line that runs on the component side from the counter chip to the via is cut. Cut the lines for: Scaler 1 Bit 5, Scaler 1 Bit 6, Scaler 1 Bit 7, Scaler 1 Bit 8, Scaler 1 Bit 9, Scaler 1 Bit 10, Scaler 1 Bit 11, Scaler 1 Bit 12, Scaler 1 Bit 13, Scaler 1 Bit 14, Scaler 1 Bit 15, and Scaler 1 Bit 16. 2. Connect bits 1:12 of Scaler #2 to the LED Driver Output Drivers for bits 5:16. Scaler #2 Bit LED Driver Output Driver Bit --------------------- -------------------------------------- bit #1 U25 pin 21 LED Driver Output Driver for Bit #5 bit #2 U25 pin 20 LED Driver Output Driver for Bit #6 bit #3 U25 pin 19 LED Driver Output Driver for Bit #7 bit #4 U25 pin 18 LED Driver Output Driver for Bit #8 bit #5 U25 pin 17 LED Driver Output Driver for Bit #9 bit #6 U25 pin 16 LED Driver Output Driver for Bit #10 bit #7 U25 pin 15 LED Driver Output Driver for Bit #11 bit #8 U25 pin 14 LED Driver Output Driver for Bit #12 bit #9 U26 pin 21 LED Driver Output Driver for Bit #13 bit #10 U26 pin 20 LED Driver Output Driver for Bit #14 bit #11 U26 pin 19 LED Driver Output Driver for Bit #15 bit #12 U26 pin 18 LED Driver Output Driver for Bit #16 15-MAY-1992 Modifications necessary for DBSC use in Level 1.5 Framework Backplane --------------------------------------------------------------------- 1. The DBSC used in the Level 1.5 Trigger Framework Backplane must have its Latch/Shift signal brought in on pins other than the Specific Backplane Bus pins corresponding to TSS #B. The Latch/Shift should come in on a typically unused Scaler Gate. Scaler #4 Gate B is chosen. A. Remove old Latch/Shift input traces Cut traces: J1-77 to U72 pin 7 (solder side) J1-78 to U72 pin 6 (solder side) B. Remove old Scaler #4 Gate B input traces Cut traces U71 pin 11 to R44-3 (R44 is never installed, so R44-3 is actually a via) U71 pin 10 to R45-3 (R45 is never installed, so R45-3 is actually a via) C. Attach Scaler #4 Gate B input to Latch/Shift receiver R44-3 to U72 pin 7 (component side) R45-3 to U72 pin 6 (component side) D. Install a 110-Ohm resistor for Scaler #4 Gate B if necessary. 5-JUN-1992 Modification so that CBus Can Never Cause the RESET of Scaler Number 2 ---------------------------------------------------------------------- Scaler number 2 on the DBSC card can be modified so that the normal CBus command to Reset this scaler has no effect. In addition DBSC scaler #2 is modified so that it will be Reset at power up. These modification can be accomplished using the following steps: 1. Disconnect the Clear Scaler #2 bar line (Clear Scl2 Bar) line that runs from U90 pin 8 to U24 pins 1 and 2. A good trace to cut is on the solder side. Leave U90 connected to the LED driver. This breaks the connection from the CBus reset command to the counters for scaler #2. 2. Connect a 33 ufd tantalum capacitor from U22 pin 1 to U22 pin 12. The positive side of the tantalum capacitor goes to U22 pin 1. 3. Connect a 1.5 k ohm resistor and a 1N4004 diode in parallel from U21 pin 1 to U21 pin 24. The cathode of the diode goes to U21 pin 24. The tantalum capacitor together with the resistor and diode cause the scaler #2 to reset on power up. 3-SEPT-1992 Modification for 10 MHz Onboard Clock and Hardware RESET of Scaler Number 1 --------------------------------------------------------------------------- Scaler number 1 on DBSC card SN 06 was modified so that it has both a hardware reset line and an onboard 10 MHz clock. This was done to Foreign Scaler #36 to monitor the location of the MR Beam with each event. First modify the DBSC Ch #1 exactly as described in the hardware reset option note above from 25-APRIL-1992. Then add the 10 MHz onboard clock as described in the following steps. 1. Disconnect the output of the the Scaler #1 Clock signal differential ECL to TTL receiver from the counter chips for Scaler #1. U69 pin 12 is the output of the Scaler #1 Clock ECL-TTL receiver. Cut this signal as it runs to U10 pin 14. Leave pin 14 of U10, U11, U12, U13, U14 and the LED driver for the Scaler #1 Clock LED all connected together, i.e. leave the clock inputs of all 5 counter chips and the Scaler #1 CLK LED driver all connected together. The output of the Differential ECL receiver for the Scaler #1 Clock signal is left un-connected. 2. Connect U10 pin 14 to U50 pin 11. A spare section of U50 (a buffer) will be used to buffer the output of the 10 MHz oscillator. Pin 11 is the output of this buffer and is connected to the clock inputs of the 5 counter chips that make up Scaler #1 and the LED driver for the Scaler #1 CLK signal. 3. Mount the 10 MHz oscillator, a 14 pin DIP, upside down between U50 and the rear connector. Connect the GND pin of the oscillator, pin 7, to the GND pin of U50, pin 10. Connect the Vcc pin of the oscillator, pin 14, to the Vcc pin of U50, pin 20. Do this by bridging a bypass capacitor across the oscillator. 4. Connect the output of the oscillator, pin 8, to the input of the buffer that is used for this signal, U50 pin 9. Now the output of the oscillator goes through a buffer and drives the clock inputs to the 5 counter chips that make up Scaler #1 and the Scaler #1 CLK LED driver. 2-JUN-1994