Reference Manual
Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 234
switch bit of the setup I-variable is set to 1 for PMAC2-style Servo ICs, or of the specified address plus
four (CHC[n+1], HMFL[n+1], +LIM[n+1], -LIM[n+1], FAULT[n+1]) if the mode switch bit of the setup
I-variable is set to 0 for PMAC-style Servo ICs. This technique is known as “parallel extension”, and can
be used with an analog incremental encoder processed through an Acc-8D Option 8 Analog Encoder
Interpolator board or its equivalent.
No Extension: In the $C method with the mode switch bit set to 0, the fractional data is always set to
zero, which means there is no extension of the incremental encoder count. This setting is used mainly to
verify the effect of one of the two extension methods. It is also recommended when feeding back the
pulse-and-direction outputs for stepper drives.
Hardware 1/T Extension: In the $C method with the mode switch bit set to 1, the fractional data is read
from a special timer-based register in the Servo IC that has already computed the fractional-count data in
hardware. This feature is supported only in the D-revision or newer (first shipments around the beginning
of 2002) of the PMAC2-style DSPGATE1 Servo ICs. The alternate timer registers for the encoder
channel must be selected by setting I7mn9 for the channel to 1.
Using this mode, permits timer-based sub-count capture and compare features to be used on this encoder
channel.
With any of these three conversion methods, the source address in the low 19 bits (bits 0 - 18) is that of
the starting register of the machine interface channel.
The first table below shows the entries for PMAC-style encoder channels. The ‘m’ in the first hex digit
(bits 20 - 23) represents the conversion method ($0, $8, or $C). For the PMAC-style channels, the bit 19
mode switch is always 0, so the second hex digit is always ‘7’ for the hardware registers.
Entries for PMAC-Style Servo ICs
Servo
IC #
Chan. 1
Chan. 2
Chan. 3
Chan. 4
Notes
0
$m78000
$m78004
$m78008
$m7800C
First IC on board PMAC
1
$m78100
$m78104
$m78108
$m7810C
Second IC on board PMAC
2
$m78200
$m78204
$m78208
$m7820C
First IC on first Acc-24P/V
3
$m78300
$m78304
$m78308
$m7830C
Second IC on first Acc-24P/V
4
$m79200
$m79204
$m79208
$m7920C
First IC on second Acc-24P/V
5
$m79300
$m79304
$m79308
$m7930C
Second IC on second Acc-24P/V
6
$m7A200
$m7A204
$m7A208
$m7A20C
First IC on third Acc-24P/V
7
$m7A300
$m7A304
$m7A308
$m7A30C
Second IC on third Acc-24P/V
8
$m7B200
$m7B204
$m7B208
$m7B20C
First IC on fourth Acc-24P/V
9
$m7B300
$m7B304
$m7B308
$m7B30C
Second IC on fourth Acc-24P/V
The next table shows the entry values for PMAC2-style encoder channels. The m in the first hex digit
(bits 20 – 23) represents the conversion method ($0, $8, or $C). The n in the second hex digit (bits 16 –
19) contains the bit 19 mode switch and the start of the source address. For methods $0 (software 1/T
extension) and $C (no extension), the bit 19 mode switch is 0, making the second hex digit 7. For method
$8 (parallel extension) or for method $C for hardware 1/T extension, the bit 19 mode switch is 1,
changing the second hex digit from 7 to F.
Entries for PMAC2-Style Servo ICs
Servo
IC #
Chan. 1
Chan. 2
Chan. 3
Chan. 4
Notes
0
$mn8000
$mn8008
$mn8010
$mn8018
First IC on board PMAC2, 3U stack
1
$mn8100
$mn8108
$mn8010
$mn8018
Second IC on board PMAC2, 3U stack
2
$mn8200
$mn8208
$mn8210
$mn8218
First Acc-24E2x, first IC on first Acc-24P/V2
3
$mn8300
$mn8308
$mn8310
$mn8318
Second Acc-24E2x, second IC on first Acc-24P/V2
4
$mn9200
$mn9208
$mn9210
$mn9218
Third Acc-24E2x, first IC on second Acc-24P/V2
5
$mn9300
$mn9308
$mn9310
$mn9318
Fourth Acc-24E2x, second IC on second Acc-24P/V2