The Model 70A is housed in a double width CAMAC module which occupies the con- trol station and adjacent normal station in the crate, thus having access to all Dataway lines. Communication with the Branch Highway is via a pair of multipin con- nectors mounted on the front panel. These two connectors are internally bridged to provide continuity of the Branch Highway through the controller, permitting all uni to be connected in a dais y-chain arrangement. In addition to its normal ON LINE op- erating mode, the controller has an OFF LINE mode which may be selected by a front panel switch. In this mode, the unit is effectively disconnected from the Branch, while remaining physically connected. Two front panel push buttons allow manual activation of Dataway Clear and Initialize in the OFF LINE mode only. Assignment of a CRATE ADDRESS to which the controller will respond, is accomplished by an in- ternal switch with visual indication of the selected address on the front panel which meets the requirements of the specification. This seven position thumbwheel switch is easily accessible from the side of the module,and may be set without the need for any tools. Several front panel indicator lights are included which should prove valuable during normal operation, and especially as an aid in trouble shooting and debugging of both hardware and software. Dataway INHIBIT may be activated via a Lemo connector which allows an external signal to be applied.
Gating is provided which gates write data onto the Dataway only during Write operations, and accepts Read data only during Read operations. This keeps the Data- way Write lines clear of data during Read operations resulting in lower Dataway noise levels. All Dataway lines have pull-up current sources in accordance with TID-25875. Pull-ups for the L lines are provided on the GL lines as per TID-25876.
Branch output lines are driven from open collector transistors capable of sinking more than the required current at low saturation voltage. Very high input imped- ance on all Branch Highway input lines results in loading far less than the max- imum permitted. The Model 70A thereby has minimal effect on Branch Highway imped- ance. This contributes to cleaner signals on these lines. The high input imped- ance is maintained with crate power off. Noise margins are improved by providing all Branch Highway input lines with threshold voltages which are higher than the usual TTL levels. Operation under adverse conditions such as high cable losses and reflections due to mismatches is thereby enhanced.
The Model 70A is capable of recognizing and executing a total of eleven dif- ferent commands addressed to the controller itself. Each of these commands imple- ments a specific operation within the controller. Among these is the ability to load a internal Station Number Register (SNR) with data from the BRW lines. Multi- station commands to preselected addresses may be accomplished by addressing the SNR, which activates Dataway stations corresponding to the data previously stored. In addition, a code is provided which addresses all stations simultaneously.
Since a Branch is not in a valid operating mode if more than one crate in the system has the same address, the Model 70A incorporates circuitry to guard against such a possibility. If a Model 70A is switched to a crate address which is already occupied, the controller will revert to the Off-line state and remain so until eith- er the other controller is switched to a different address(or off-line), or another valid address is selected. This feature is particularly useful when a Branch has crates in remote locations from each other, and will prevent interference to an op- erating system if an incorrect address is chosen.
While the basic timing requirements are defined by the CAMAC specifications, considerable latitude is permitted and in some cases the timing is either not spec- ified, or not clear and open to interpretation. The Model 70A has been designed us- ing "CERN Preferred Values" as a guideline which sets tighter tolerances on the tim- ing within the broader CAMAC specifications. This results in a controller capable of operating with optimum performance and small variations from unit to unit. The Model 70A features a precision clock generator which assures accurately timed steps throughout each timing sequence. The clock is started and stopped as required; no time being lost due to having to synchronize the clock to branch signals as would be necessary with a gated free running oscillator. Branch operations at the maxi- mum rate permitted are thus achieved.
2.1 CONTROLS, INDICATORS, AND CONNECTORS 2.1.1 FRONT PANEL CONTROLS ON LINE-OFF LINE Switch Selects On Line or Off Line Mode. C Pushbutton(effective in Off Line only) Generates Dataway cycle with C, Sl, S2, B. Z Pushbutton(effective in Off Line only) Generates Dataway cycle with Z, S1, S2, B. Sets I flip flop.(Dataway I will assume a maintained logic 1 state when controller is returned to the On Line mode). I Input(effective in On Line and Activates Dataway Inhibit line when CAMAC Off Line) Logic 1 applied. Input load = 1 TTL input. 2.1.2 FRONT PANEL INDICATORS ON LINE Indicator Illuminated when controller is in On Line state. CONTROLLER ADDRESSED Indicator Illuminated during an operation addressed to controller. N(28) + N(30) (TA+TB) BRANCH OPERATION Indicator Illuminated during any operation initiate from the Branch Highway.(TA+TB+BZ) G Indicator Illuminated during a Graded-L operation. G(TA+TB) D Indicator Illuminated when one or more Look at Me demands(GL's) are present. I Indicator Illuminated wherever Dataway I is at a Logic 1. NOTE: Controller Addressed, Branch Operation, and G Indications are stretched so short duration-signals are visible. 2.1,3 FRONT PANEL CONNECTORS BRANCH HIGHWAY PORTS(2) 132 contact connectors-Hughes WSS0132S00BN 2.1.4 INTERNAL CONTROL CRATE ADDRESS Switch Assigns crate address to which controller will respond. Switch is set with visual indication on front panel. 2.1.5 REAR PANEL CONNECTOR LAM GRADER 52 contact connector-Cannon 2DB52P 2.2 SIGNAL STANDARDS 2.2.1 BRANCH HIGHWAY SIGNALS 220.127.116.11 INPUTS BA,BF,BN,BCR,BRW,BZ,BTA,BV4 Threshold voltage +1.8v typical Input current <+10uA @ +0.3v,+50uA @ +4.lv typical 18.104.22.168 OUTPUTS BQ,BX,BD,BTB,BRW Logic 1 voltage +0.3v max. @ 133ma Current sinking capability 133ma min. 22.214.171.124 TIMING Command Mode Timing Cycle 1450ns typical (see figure 2-1) Graded-L Mode Timing Cycle 1050ns typical 2.2.2 DATAWAY SIGNALS 126.96.36.199 INPUTS' R,Q,X,L,P2 Threshold voltage +1.1v typical Pull up capability 10.2ma max. @ +0.5v Current source 2.6ma max. @ +3.5v 188.8.131.52 OUTPUTS W,A,F,B,Z,C,l N S1,S2 Current sinking capability 0.5v 39.4 max. 7.4 max. 56.Oma max. Pull up capability @ 3.5v 2.6 max. 2.6 max. 12.6ma max. 184.108.40.206 TIMING Dataway cycle 1.1uS typical Sl,S2 Pulse width 220ns typical 2.3 COMMANDS IMPLEMENTED ACTION COMMAND RESPONSE 1. Generate Dataway Z N(28)A(8)F(26) BQ=O 2. Generate Dataway C N(28)A(9)F(26) BQ=O 3. Read GL N(30)A(0-7)F(O) BQ=l 4. Load SNR N(30)A(8)F(16)-Sl BQ=l 5. Remove Dataway I N(30)A(9)F(24)-S1 BQ=O 6. Set Dataway I N(30)A(9)F(26)-Sl+(Z-S2) BQ=O 7. Test Dataway I N(30)A(9)F(27) BQ=l if I 1 8. Disable BD Output N(30)A(10)F(24)-Sl+(Z-S2) BQ=O 9. Enable BD Output N(30)A(1O)F(26)-Sl BQ=O 10. Test BD Output Enabled N(30)A(10)F(27) BQ=l if BD enabled 11. Test Demands Present N(30)A(11)F(27) BQ=l if demands present NOTES: 1. All commands are accepted only in response to BTA. BX is generated for each. 2. A Dataway cycle with Sl,S2 and B is generated for commands 1 and 2 only. Dataway I is generated in response to Z-S2 and maintained until reset. 3. In addition to the above, N(24) activates all addresses stored in Station Number Register(SNR), and N(26) activates all Stations simultaneously. 2.4 BRANCH HIGHWAY LINE USEAGE BCR-1-7 Crate Address(BCRi) to which On Line controller responds. BCRi = BCR line corresponding to selected crate address. BTA Initiates handshake and starts cycle in addressed crate. Internal TA is conditioned (integrated)approximately lOOns to suppress noise. TA = BCRi-BTA BTB 1-7 On line, unaddressed controller has BTBi line at logic 1, all other BTB lines at logic 0. Addressed controller generates internal TB at appropriate time in cycle. BTBi = 0 generated in response to TB. All BTB lines in Off Line controllers are at Logic 0. BTBi = BTB.line corresponding to selected crate address. BTB lines have controlled transition times of approximately 100ns. BRW 1-24 Data on BRW lines is gated onto corresponding Dataway W lines during write operations, F(16-23) (TA+TB). Data on Dataway R lines are gated onto corresponding BRW lines during read operations, F(O-7)(TA+TB). BZ Generates Dataway cycle with Sl,S2,B, and Z. Sets Dataway I to maintained logic 1 state. BZ is integrated for approximately 3us, and takes pre- cedence over all other signals in the Branch, i.e., any cycle in progress is terminated, and a new BTA will not be accepted for the duration of BZ. BG When BG is present, a Graded-L operation is initiated in response to BTA. Internal G = BCRi-BG. BA1,2,4,8Gated onto corresponding Dataway A lines during controller cycle,(TA+TB). BF1,2,4 Gated onto corresponding Dataway F lines during controller cycle,(TA+TB). 8,16 BN1,2,4 Decoded by controller and gated onto appropriate Dataway N line during 8,16 command mode controller cycle, G' (TA+TB). BQ Dataway Q, and Q signals generated by the controller are gated onto the BQ line during a controller cycle,(TA+TB). BX Dataway X, and X signals generated by the controller are gated onto the BX line during a controller cycle, (TA+TB). BD BD is generated when an internal demand(D) signal is present(as a result of one or more GL lines at logic 1) and BD is enabled. BD has controlled transition time of approximately 100ns. BV4 Controller generates a "Fast Read" short cycle in response to BTA when BV4 is at logic 1. BV4 must be activated by user by addition of a jumper wire on circuit board. BSC Cable shield grounding conductors(2). Grounded internally by means of jumpers which may be removed if desired.