Reference Manual
Turbo PMAC/PMAC2 Software Reference
Turbo PMAC Global I-Variables 252
The final digit, represented by an x in both of these tables, can take a value of 0 to 5, depending on which
I/O point on the board is used for the LSB:
x=0: I/O00-07 I/O48-55 I/O96-103
x=1: I/O08-15 I/O56-63 I/O104-111
x=2: I/O16-23 I/O64-71 I/O112-119
x=3: I/O24-31 I/O72-79 I/O120-127
x=4: I/O32-39 I/O80-87 I/O128-135
x=5: I/O40-47 I/O88-95 I/O136-143
Width/Offset Word: The second setup line (I-variable) of this parallel read entry contains information
about what data is to be read starting at the base address. This 24-bit value, usually represented as 6
hexadecimal digits, is split into four parts, as shown in the following table.
Hex Digit
1
2
3
4
5
6
Contents
2 or 3
Bit Width
Byte
LSB Location
The first hex digit contains a 2 or a 3. If it has a 2, there is no filtering of the data, and the entry is a 2-line
entry. If it has a 3, the input data is filtered to protect against noise or data corruption, and the entry is a
3-line entry, with the third line controlling the filtering.
The second and third digits represent the width of the parallel data in bits, and can range from $01 (1 bit
wide – not of much practical use) to $18 (24 bits wide). If the value of these digits is from $01 to $08,
only the base address in the first line is used. If the value of these digits is from $09 to $10 (16), the base
address and the next higher-numbered address are used. If the value of these digits is from $11 to $18 (17
to 24), three addresses starting at the base address are used.
The fourth digit represents which byte of the source words is used. It has three valid values:
0: Low byte (bits 0 – 7)
1: Middle byte (bits 8 – 15)
2: High byte (bits 16 – 23)
The fifth and sixth digits contain the bit location of the LSB of the data in the source word at the base
address, and can range from $00 (Bit 0 of the source address is the LSB), through $07 (Bit 7 of the source
address is the LSB). To calculate this value, divide the number of the I/O point used for the LSB by 8
and use the remainder here. For example, if I/O19 is used for the LSB, the remainder of 19/16 is 3.
Maximum Change Word: If the method character for a parallel read is $3 or $7, specifying filtered
parallel read, there is a third setup line (I-variable) for the entry. This third line contains the maximum
change in the source data in a single cycle that will be reflected in the processed result, expressed in LSBs
per servo cycle. The filtering that this creates provides an important protection against noise and
misreading of data. This number is effectively a velocity value, and should be set slightly greater than the
maximum true velocity ever expected.
Resolver Conversion Entry ($F/$4): An ECT entry in which the first hex digit of the first line is $F and
the first hex digit of the second line is $4 converts the result of a pair of resolver sine/cosine A/D
converters (ADCs) to a resolver angle value with 14-bit resolution.
The $E entry converts the sine and cosine resolver feedback values processed through the Geo PMAC’s
A/D converter (ADC) registers to a 14-bit resolver angle value.
Method/Address Word: The first setup line of a resolver conversion entry contains $F in the first hex digit
and the Y-address of the first ADC register to be read in the low 19 bits (bits 0 – 18). The next ADC
register is read at the next higher Y-address. If bit 19 of the line is set to 0, the conversion creates a
“clockwise” rotation sense. If bit 19 of the line is set to 1, the conversion creates a “counter-clockwise”
rotation sense.
For example, if the first ADC register is at Y:$078C00, the first line would be set to $F78C00 for a
clockwise rotation sense, or to $FF8C00 for a counterclockwise rotation sense.