Accessory 24E2S
Hardware Setup
10
opposite: when one is high, the other is low. If for some reason, such as a cable connection coming
undone, one or more of the signal lines is no longer driven, pull-up resistors on the input line pull and
hold the signal high.
The encoder-loss detection circuitry uses exclusive-or (XOR) gates on each complementary pair to detect
whether the signals are in the same or opposite states. These results are combined to produce a single
encoder-loss status bit that the processor can read.
In order to enable this function, the socketed resistor packs for the encoder must be reversed from their
factory default setting so that the complementary encoder lines A/, B/, and C/ are pulled up to 5V instead
of pulled to 2.5V. The resistor packs to be reversed are RP19, RP21, RP27, and RP29.
Acc-24E2S Discrete On-board Logic with UMAC Turbo CPU
Channel
Resistor
Pack
Status Bit Address (Even-
Numbered Servo IC)*
Status Bit Address (Odd-
Numbered Servo IC)*
Status
Bit Name
Bit Error
State
1
RP19
Y:$07xF08,5
Y:$07xF0C,5
QL_1-
0
2
RP21
Y:$07xF09,5
Y:$07xF0D,5
QL_2-
0
3
RP27
Y:$07xF0A,5
Y:$07xF0E,5
QL_3-
0
4
RP29
Y:$07xF0B,5
Y:$07xF0F,5
QL_4-
0
*The x digit in this hex address matches the value (8, 9, A, or B) in the fourth digit from the right in the board’s own
base address (e.g. $079200). If alternate addressing of Servo ICs is used (e.g. Servo IC 2*), add $20 to these addresses.
Acc-24E2S Discrete On-board Logic with UMAC MACRO CPU
Channel
Resistor
Pack
Status Bit Address (First-
Servo IC)*
Status Bit Address
(Second Servo IC)*
Status Bit
Name
Bit Error
State
1
RP19
Y:$B8C8,5
Y:$B8EC,5
QL_1-
0
2
RP21
Y:$B8C9,5
Y:$B8ED,5
QL_2-
0
3
RP27
Y:$B8CA,5
Y:$B8EE,5
QL_3-
0
4
RP29
Y:$B8CB,5
Y:$B8EF,5
QL_4-
0
*First Servo IC has base address $C040; second Servo IC has base address $C060.
Position Compare Port Driver IC
As with the other PMAC controllers, the UMAC has the high speed compare outputs allowing the firing
of an output based on position. This circuit will fire within 100 nsec of reaching the desired position.
The position compare output ports on Acc-24E2S have driver IC at components U29 and U30. This IC
gives a fast CMOS driver.
The following table lists the properties of each driver IC:
Part
# of Pins
Max Voltage and Current
Output Type
Max Frequency
DS75451N
8
5V, 10 mA
Totem-Pole
(CMOS)
5 MHz
