IC-LNB_16 Datasheet, PDF (29/37 Pages) IC-Haus GmbH – 18-BIT OPTO ENCODER

iC-LNB 18-BIT OPTO ENCODER ^preliminary
WITH SPI AND SER/PAR INTERFACES
FLEXCOUNT^®
Rev B2, Page 29/37
When FlexCount is enabled in iC-LNB, the resolution
can be freely programmed and is output through the
incremental signals. Another option is to output the
set resolution through the SPI interface and the shift
register, or, in parallel encoder mode, to the parallel IO
ports. FlexCount operates in real time and does not
introduce any significant latency to the signal path.
Enable/disable
FlexCount can be enabled using register bit NENFLEX.
SELABS determines whether the FlexCount resolution
or iC-LNB’s maximum internal resolution (dependent on
RESIPO) is output for the absolute data output (parallel
encoder mode, shift register or SPI).
RESSUB Addr. 0x0F; 0x10; 0x11 bit 3:0
Code
Resolution (edges per revolution)
0x3
4
0x7
8
...
....
0x0FFFF 65536
...
... (only with 7/8 bit interpolation)
0x1FFFF 131072 (only with 7/8 bit interpolation)
...
... (only with 8 bit interpolation)
0x3FFFF 262144 (only with 8 bit interpolation)
NB: RESSUB = resolution - 1
Resolution must be divisible by four
Max. resolution is limited by the interpolator resolution RESIPO
Table 32: FlexCount resolution
NENFLEX
Code
0
1
Addr. 0x0B; bit 1
Description
FlexCount enabled
FlexCount disabled
Table 30: FlexCount disable
Reset
FlexCount must be stopped before the resolution or
direction of rotation are reprogrammed (pin DIR or reg-
ister bit DIR). This is done using register bit STOPFLEX.
This freezes the FlexCount outputs and FlexCount goes
into its reset state. After STOPFLEX has been reset
the outputs are enabled and FlexCount moves to the
current position.
SELABS
Code
0
1
Addr. 0x0B; bit 2
SER/PAR/SPI interface
FlexCount resolution
Maximum resolution*
*16 bit, 17 bit, 18 bit dependent on RESIPO
Table 31: SPI, SER, PAR absolute output options
STOPFLEX
Addr. 0x11; bit 5
Code
Description
0
Normal operation
1
FlexCount stopped
FlexCount reset: STOPFLEX 1 → 0
Table 33: FlexCount reset
Resolution
Parameter RESSUB defines the FlexCount resolution.
The binary value in RESSUB is equivalent to the re-
quired resolution minus 1; for instance, RESSUB must
be programmed to 0x0FFFF (binary value for 65,535)
for a resolution of 65,536 steps (a 16-bit resolution).
The required resolution must be divisible by four and
the maximum resolution is limited by the set interpola-
tor resolution. At an interpolation of 6 bits FlexCount
may have a maximum resolution of 65,536 (RESSUB =
0x0FFFF); at 7-bit interpolation this maximum rises
to 131,072 (RESSUB = 0x1FFFF), and at 8 bits to a
full resolution of 262,144 (RESSUB = 0X3FFFF). Flex-
Count is always output in Gray code for all settable
resolutions. With non-binary resolutions the Gray code
is capped symmetrically to 0. This retains the required
single-step transitions of the Gray code.
Following a reset (STOPFLEX 1 → 0) FlexCount
searches for the current position. During this position
signals/data are not valid. Attainment of the current
position and thus valid output signals are indicated in
the status register with POSOK.
POSOK
Code
0
1
Addr. 0x12; bit 0
Description
Position invalid
Position valid
Table 34: Position valid
NB: In order to avoid infinite loops e.g. in case
of glitches or communication errors, the query for
POSOK should be aborted after a defined waiting pe-
riod of 30 ms (up to 1000 RPM) to initiate a restart
(cue defensive programming for safety requirements).
After e. g. 5 restarts a configuration error should be
reported.