Interfaces SSI Absolute Position Values

incremental signals with 1-V The absolute position value beginning with the Most Signifi cant Bit (MSB fi rst) is transferred on the DATA lines in synchronism with a CLOCK signal transmitted by the control. The SSI standard data word length for singleturn absolute encoders is 13 bits, and for multiturn absolute encoders 25 bits. In addition to the absolute position values, sinusoidal InterfaceSSI serial Data transfer Absolute position valuesData inputDifferential line receiver according to EIA standard RS-485 for the CLOCK and CLOCK signalsData outputDifferential line driver according to EIA standard RS 485 for the DATA and DATA signalsCodeGrayAscending position valuesWith clockwise rotation (viewed from fl ange side)(can be switched via interface) Incremental signals 1 V
PP levels are transmitted. For signal description see
PP .For the ECN/EQN 4xx and ROC/ROQ 4xx rotary encoders, the following • functions can be activated via the programming inputs of the interfaces by applying the supply voltage U Incremental signals 1 V
PP (see Incremental Signals 1 V
PP ) Continuous application of a HIGH level to pin 2 reverses the direction of rotation for ascending position values. Zero reset (setting to zero)Applying a positive edge (t
P : Programming inputs Direction of rotation InactiveActive Switching timeDirection of rotation and zero reset (for ECN/EQN 4xx, ROC/ROQ 4xx) LOW < 0.25 x U
P HIGH > 0.6 x U
P t
min > 1 ms • Connecting cable
min > 1 ms) to pin 5 sets the current position to zero.
2 ) + 4(2 x 0.14 mm
2 ) + (4 x 0.5 mm
2 )]Max. 150 m at 90 pF/m distributed capacitance 6 ns/m Cable lengthPropagation timeShielded HEIDENHAIN cablePUR [(4 x 0.14 mm Note: The programming inputs must always be terminated with a resistor (see input circuitry of the subsequent electronics). Control cycle for complete data format In the quiescent state the clock and data lines are at HIGH level. The current position value is stored on the fi rst falling edge of the clock. The stored data is then clocked out on the fi rst rising edge.After transmission of a complete data word, the data line remains low for a period of time (t
T = 1 to 10 µst cal see Specifi cations t 1 0.4 µs (without cable)t 2 = 17 to 20 µs forECN/EQN 4xx ROC/ROQ 4xx 12 to 30 µs for ECN/EQN 10xx ROC/ROQ 10xxn = Data word length13 bits with ECN/ ROC 2 ) until the encoder is ready for interrogation of a new value. If another data-output request (CLOCK) is received within this time, the same data will be output once again.If the data output is interrupted (CLOCK = high for t t CLOCK and DATA not shown Permissible clock frequency with respect to cable lengths
2 ), a new position value will be stored on the next falling edge of the clock, and on the subsequent rising edge clocked out to the subsequent electronics.
Cable length [m] Clock frequency [kHz] Data transfer

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