6.7.5 Sin/Cos / TTL X8
6.7.5.1 TTL encoder
Ch3: TTL(3) - TTL signals
TTL encoders are ...
a. ... usually pure incremental encoders
without
an absolute value interface. In
this case,
P 570[0] - ENC_CH3_Abs
must be set to OFF(0).
b. ... in a few exceptional cases, incremental encoders
with
an SSI absolute
value interface. In this case,
P 570[0] - ENC_CH3_Abs
must be accordingly
set to SSI(1) so that it will be possible to read the absolute encoder position
for the absolute value initialization routine once during the initialization
phase.
6.7.5.1.1 Pure TTL incremental encoder
Set P 507[0] - ENC_CH3_Sel to TTL(3) and P 570[0] - ENC_CH3_Abs to OFF(0)
when using pure TTL encoders, i.e. encoders without an absolute value interface but
with a TTL zero pulse.
Linear TTL encoders are run as rotary encoders. For linear motor operation, P 572
[0] - ENC_CH3_Lines and the encoder gearing (see the “Encoder gearing” section)
are used to establish the ratio for the linear motor’s pole pair subdivision (North-
North) for commutation. 1 x North-North corresponds to one revolution from Lines. In
this case, the motor pole pair number must be set to 1. P 582[0] - ENC_CH3_
PeriodLen is not used in this case.
The TTL interface accepts various TTL signal types, which can be selected using
P 2824[0] - ENC_CH3_TTL_SignalType:
(0)AF_B - A/B tracks (forward counting, X4 encoding) - AB
(1)AR_B - A/B tracks (reverse counting, X4 encoding) - AB_inv
MOOG
ID
No.:
CB40859-001
Date:
02/2018
MSD Servo Drive - Device Help
81
6 Encoder
(2)ABDFN - A: Clock (falling edge), B: Direction (1 = positive) - PulseDir
(3)ABDRP - A: Clock (rising edge), B: Direction (1 = negative) - PulseDir_inv
(4)reserved
A maximum interpolation period, in ms (milliseconds), can be configured for the TTL
interface using
P 602[0] - ENC_CH3_Period
. Within this context,
Period
is the
maximum time of “no activity” since the last TTL counter event:
Period = 0: Function disabled (default)
Period > 0 (= n ms): If no counter event is registered in n ms, the speed will
be set to 0.
Zero pulse
There is no parameter for activating the zero pulse evaluation here, as this
evaluation is controlled exclusively based on the homing mode (see Section
"Homing" on page 18
). However, setting P 571[0] - ENC_CH3_NpTest to 1
provides a test mode that can be used during commissioning in order to be able to
activate the zero pulse evaluation even without homing. Scope signals 1034 and
1036 can be used to view a received zero pulse within this context. This test mode
must be disabled during normal operation (P 571[0] = 0).
Commutation
Motor operation with pure incremental encoders needs for the auto commutation
function to be enabled without fail. For details, see Section "Synchronous motor
auto commutation" on page 1
6.7.5.1.2 TTL incremental encoder with SSI absolute value
interface
See Section "Sin/Cos incremental encoder with absolute value interface" on
page 82 and in special Section "SSI absolute value interface" on page 84.
