Reference Manual

Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 204
If I68n0/I69n0 is set to 8, the decoder inputs the pulse and direction signal generated by Channel n's pulse
frequency modulator (PFM) output circuitry. This permits the PMAC2 to create a phantom closed loop
when driving an open-loop stepper system. No jumpers or cables are needed to do this; the connection is
entirely within the MACRO IC. The counter polarity automatically matches the PFM output polarity.
If I68n0/I69n0 is set to 11 or 15, Channel n is expecting three Hall-sensor format inputs on CHAn, CHBn,
and CHCn, each with approximately 50% duty cycle, and approximately one-third (120
o
e) of a cycle out
of phase with each other. The decode circuitry will generate one count on each edge of each signal,
yielding six counts per signal cycle (x6 decode). The difference between 11 and 15 is which direction of
signal causes the counter to count up.
If I68n0/I69n0 is set to 12, the timer circuitry is set up to read magnetostrictive linear displacement
transducers (MLDTs) such as Temposonics
TM
. In this mode, the timer is cleared when the PFM circuitry
sends out the excitation pulse to the sensor on PULSEn, and it is latched into the memory-mapped
register when the excitation pulse is received on CHAn.
I68n1/I69n1 MACRO IC Channel n* Position Compare Channel Select
Range: 0 - 1
Units: None
Default: 0
Note:
This I-variable is active only if the MACRO IC is present, and is a DSPGATE2 IC.
The presence and type of MACRO ICs are reported in I4902 and I4903.
I68n1 and I69n1 control which channel’s encoder counter is tied to the position compare circuitry for
Channel n* (n* = 1 to 2) on a “DSPGATE2” MACRO IC is decoded into counts. For MACRO ICs 0 and
2, n = n*; for MACRO ICs 1 and 3, n = n* + 5 (i.e. I6811 controls MACRO IC 0 Channel 1; I6971
controls MACRO IC 3 Channel 2). They have the following possible settings:
 I68n1/I69n1 = 0: Use Channel n* encoder counter for position compare function
 I68n1/I69n1 = 1: Use Channel 1* encoder counter on IC for position compare function
When I68n1/I69n1 is set to 0, Channel n*’s position compare registers tied to the channel’s own encoder
counter, and the position compare signal appears only on the EQU output for that channel.
When I68n1/I69n1 is set to 1, the channel's position compare register is tied to the first encoder counter
on the MACRO IC, and the position compare signal appears both on Channel n*’s EQU output, and
combined into the EQU output for Channel 1* on the MACRO IC (EQU1* on the board); executed as a
logical OR.
I68n1 for the first channel performs no effective function, so is always 1. It cannot be set to 0.
Note:
By default, the position compare circuitry on a MACRO IC is not used on Turbo
PMAC2 boards. The compare outputs are the alternate use of lines on the
Multiplexer port.
I68n2/I69n2 MACRO IC Encoder n* Capture Control
Range: 0 - 15
Units: none
Default: 1
Note:
This I-variable is only active if the MACRO IC is present, and is a DSPGATE2 IC.
The presence and type of MACRO ICs are reported in I4902 and I4903.