Ssi Interface; Principle - Balluff BTL7-S5 Betriebsanleitung

BTL7-S5 _ _ (B)-M _ _ _ _ -A/B/Y/Z(8)-S32/S115/S140/S147/KA _ _ /FA _ _
Micropulse Transducer - Rod Style
6

SSI interface

6.1

Principle

SSI stands for Synchronous Serial Interface and describes
a digital synchronous interface with a differential clock line
and a differential data line.
With the first falling cycle edge, the data word to be output
is buffered in the BTL7 to ensure data consistency. Data
output takes place with the first rising cycle flank, i.e. the
transducer supplies a bit to the data line for each rising
cycle edge. In doing so, the line capacities and delays of
drivers t when querying the data bits must be taken into
v
account in the controller.
The max. clock frequency f
length (see Technical data on page 20, Fig. 8-2). The t
time, also called monoflop time, is started with the last
falling edge and is output as the low level with the last
rising edge. The data line remains at low until the t
has elapsed. Afterwards, the BTL7 is ready again to
receive the next clock package.
SSIn
T
Clk
Clk
1
Data
MSB
T
Clk
Clk
t
Data
Clk
Data
T = 1/f SSI clock period, SSI clock frequency
Clk Clk
T = 1/f Sampling period, sampling rate
A A
n Number of bits to be transmitted (requires n+1 clock impulses)
t = 2 · T Time until the SSI interface is ready again
m Clk
t = 150 ns Transmission delay times (measured with a 1 m cable)
v
14 english
is dependent on the cable
Clk
m
time
m
2 3 4 5
t
v v
T
A
With the BTL7, position data is determined and output in a
timely manner and synchronous to the external sampling
period. For synchronous operation, the sampling period T
must be in the range T
A,min
switches to asynchronous operation outside of this range.
If the minimum sampling time is undercut, the BTL7
outputs the same position value several times. The
external sampling rate is then greater than the internal rate.
In addition, T must be long enough so that the next clock
A
package does not occur in the t
package.
t
m
n n+1
LSB
≤ T ≤ 16 ms. The BTL7
A
range of the previous
m
A