6.5.4 Sin/Cos / TTL X7
6.5.4.1 TTL encoder
Ch1: TTL(3) - TTL signals
TTL encoders are ...
a. ... ... usually pure incremental encoders
without
an absolute value interface.
In this case,
P 540[0] - ENC_CH1_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 540[0] - ENC_CH1_Abs
must be accordingly
set to SSI(1) (SSI_CONT(4) in special cases), so that it will be possible to
read the absolute encoder position for the absolute value initialization
routine once during the initialization phase.
6.5.4.1.1 Pure TTL incremental encoder
Set P 505[0] - ENC_CH1_Sel to TTL(3) and P 540[0] - ENC_CH1_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 542
[0] - ENC_CH1_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. Moreover, P 553[0] - ENC_
CH1_PeriodLen is not used in this case.
The TTL interface accepts various TTL signal types, which can be selected using
P 558[0] - ENC_CH1_TTL_SignalType:
l
(0)AF_B - A/B tracks (forward counting, X4 encoding) - AB
l
(1)AR_B - A/B tracks (reverse counting, X4 encoding) - AB_inv
MOOG
ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
63
6 Encoder
l
(2)ABDFN - A: Clock (falling edge), B: Direction (1 = positive) - PulseDir
l
(3)ABDRP - A: Clock (rising edge), B: Direction (1 = negative) - PulseDir_inv
l
(4)reserved
A maximum interpolation period, in ms (milliseconds), can be configured for the TTL
interface using P 601[0] - ENC_CH1_Period. Within this context, Period is the
maximum time of “no activity” since the last TTL counter event:
l
Period = 0: Function disabled (default)
l
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 249). However, setting P 541[0] - ENC_CH1_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 1014 and
1016 can be used to view a received zero pulse within this context. This test mode
must be disabled during normal operation (P 541[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
6.5.4.1.2 TTL incremental encoder with
SSI absolute value interface
See Section "Sin/Cos incremental encoders with absolute value interface" on page
65 and in specialSection "SSI absolute value interface" on page 67.
