Rockwell Automation 1771-SF1 SERVO INT MOD - Manual (Page 17)

Programming and Operation
Chapter 3
3Ć5
A low = TRUE signal is transmitted to status port bit 0 after the marker
signal is latched by the servo interface module for each completed
revolution of the encoder shaft. A write instruction to 600AH will reset
this latched output.
A low = TRUE signal appears at status port bit 1 whenever the target
value (preset) is greater than the accumulated value of the counters
counting the encoder pulses. The bit goes high when the accumulated
value becomes equal to or greater than the target value.
Generally, a low signal appears at status port bit 2 when the rotation of the
encoder shaft is counterclockwise (CCW). A high signal will then
indicate clockwise (CW) rotation. This relationship depends on system
hardware and/or wiring polarity.
Whenever the accumulated value of the encoder counter becomes equal to
the target value preset, an interrupt signal is sent to the micro controller.
The vectored interrupt is generated by the counter/timer circuit (CTC
Channel 2) in the micro controller. The interrupt condition is
automatically reset by the micro controller during execution of the return
from interrupt instruction (RETI). The micro controller must be
programmed to perform this function.
The servo interface module controls the drive package in accordance with
commands received from the micro controller module. All programming
of the micro controller is written in the Z-80 instruction set. In order to
transfer the information described in Paragraph 3.1 from or to the servo
interface module, certain memory addresses have to be accessed in the
micro controller.
Whenever a Z-80 instruction is written to or read from a control function
address for the servo interface module, the instruction will force low one
of the corresponding special enable lines, DSEN 10-17. This signal
instructs the servo interface module to latch data received from the 8-bit
bidirectional backplane data bus (system write) or to place data on the
data bus (system read). The control functions, their addresses and
corresponding DSEN lines are tabulated in Table 3.B.
Marker
A > B
CCW/CW
Target Value Interrupt
Programming the Servo Control
Functions