IC-LNB_13 Datasheet, PDF (28/35 Pages) IC-Haus GmbH – 18-BIT OPTO ENCODER WITH SPI AND SER/PAR INTERFACES

iC-LNB 18-BIT OPTO ENCODER ^preliminary
WITH SPI AND SER/PAR INTERFACES
FLEXCOUNT^®
Rev A1, Page 28/35
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 reg-
ister, 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 NEN-
FLEX. 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).
NENFLEX
Code
0
1
Addr. 0x0B; bit 1
Description
FlexCount enabled
FlexCount disabled
Table 30: FlexCount disable
RESSUB Addr. 0x0F; 0x10; 0x11 bit 3:0
Code
Resolution (edges per revolution)
0x3
4
0x7
8
...
RESSUB + 1
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
Table 32: FlexCount resolution
Reset
FlexCount must be stopped before the resolution or di-
rection of rotation are reprogrammed (pin DIR or regis-
ter 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 res-
olutions. 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
The FlexCount output signals can be set to low using
register bit NOUTLO; FlexCount itself continues to run.
This function should be used after FlexCount has been
reset to prevent the device ’running’ to the current po-
sition in the output signals.