User's Manual

PMAC User Manual
68 Setting Up a Motor
Incremental Encoder Entries
Incremental encoders are converted with one of the conversion formats $0x, $8x, or $Cx. The low sixteen
bits of the setup word specify the address of the source on the X data bus. For incremental encoders, the
source address must be one of the DSPGATE encoder counters, selected from the following list:
ENC1: $C000 ENC9: $C020
ENC2: $C004 ENC10: $C024
ENC3: $C008 ENC11: $C028
ENC4: $C00C ENC12: $C02C
ENC5: $C010 ENC13: $C030
ENC6: $C014 ENC14: $C034
ENC7: $C018 ENC15: $C038
ENC8: $C01C ENC16: $C03C
Use the addresses from this list even though the actual encoder counter register has an address two higher.
Incremental Encoder Conversion
X-Word:
Converted Position Data
Y-word:
Source and Processing of Data
Bits 0-4: Fractional Bits Bits 0-15: Word address of source data
Bits 5-23: Integer Bits Bits 16-23: Conversion format
$00 = 1/T interpolation
$80 = parallel-bit interpolation
$C0
= no interpolation
The source counter already reflects the method of decoding the incoming quadrature or pulse-and-
direction waveform — whether there are one, two, or four counts per cycle. The decode method is
determined by Encoder I-variable 0 (I900, I905, etc.) for that encoder. One bit in the counter is a count,
whether it represents a full, half, or quarter wave cycle.
1/T Interpolation
Most people will use the 1/T-extension conversion method ($0x), which uses timers associated with each
counter to estimate fractional resolution (see previous illustration). A typical setup word for this would
be $00C008, which provides 1/T-extension conversion of the encoder 3 counter.
Parallel-Bit Interpolation
If the set up uses the parallel sub-count interpolation for incremental feedback, use the $8x conversion
format. In this case, the source address must be one of the odd-numbered encoders. A typical setup word
in this case would be $80C010, which provides parallel extension of the encoder 5 counter using
encoder 6’s flags.
No Interpolation
For conversion without any sub-count interpolation, the $Cx conversion format should be used. A typical
setup word in this case would be $C0C00C, which provides a non-interpolated conversion of the encoder
4 counter.
Acc-28 Analog-to-Digital Conversion Register Entries
The $1x conversion format picks up data from the top 16 bits of a 24-bit word. It is intended for use with
the A/D converter registers in the DSPGATEs, which are fed by Accessory 23 (obsolete) or Accessory
28. (When using the Acc-36 A/D converter board, treat the data as 12-bit parallel-format data.) The
source address specifies a word in the Y memory space, and should be one of the following: