User's Manual

PMAC2A PC104 Hardware Reference Manual
Machine Connections 9
MACHINE CONNECTIONS
Typically, the user connections are made to terminal blocks that attach to the JMACH connectors by a
flat cable. The following are the terminal blocks recommended for connections:
• 34-Pin IDC header to terminal block breakouts (Phoenix part number 2281063) Delta Tau
part number 100-FLKM34-000
• 50-Pin IDC header to terminal block breakouts (Phoenix part number 2281089) Delta Tau
part number 100-FLKM50-000
Mounting
The PMAC2A PC/104 is typically installed using standoffs when stacked
to a PC/104 computer or as a stand-alone controller. At each of the four
corners of the PMAC2A PC/104 board, there are mounting holes that can
be used for this.
The PMAC2A PC/104 CPU is placed always at the bottom of the stack.
The order of the Acc-1P or Acc-2P with respect to the CPU does not
matter.
Power Supplies
Digital Power Supply
3A @ +5V (±5%) (15 W) with a minimum 5 msec rise time
(Eight-channel configuration, with a typical load of encoders)
The PMAC2A PC/104, the Acc-1P and the Acc-2P each require a 1A @ 5VDC power supply for
operation. Therefore, a 3A @ 5VDC power supply is recommended for a PMAC2A PC/104 board
stack with Acc-1P and Acc-2P boards.
• The host computer provides the 5 Volts power when installed in the PC/104 bus and cannot
be disconnected. In this case, there must be no external +5V supply, or the two supplies will
"fight" each other, possibly causing damage. This voltage could be measured on the TB1
terminal block or the JMACH1 connector.
• In a stand-alone configuration, when PMAC is not plugged in a computer bus, it will need an
external 5V supply to power its digital circuits. The 5V power supply can be brought in
either from the TB1 terminal block or from the JMACH1 connector.
• When an ACC-2P is used, a minimum rise time of 5 msec is a requirement of the power
supply. In addition, the power supply ramp-down time should not exceed 20 msec. While
solutions to this issue can involve complex circuitry that minimizes power loss during normal
operation, the simplest method of quickly bringing down the power rail is to add a bleed-
down resistor between VCC and GND. The resistor should be large enough that it does not
cause unnecessary power consumption, while still discharging the bulk capacitance as
quickly as possible. Specific resistor values will depend on the overall design of the system,
but in general the voltage drop-off time should not exceed 20 msec. A value that has been
found to work for some systems is 18k.
DAC Outputs Power Supply
0.3A @ +12 to +15V (4.5W)
0.25A @ -12 to -15V (3.8W)
(Eight-channel configuration)
• The host computer provides the ±12 Volts power supply in the case PMAC is installed in the
PC/104 bus. With the board stack into the bus, it will pull ±12V power from the bus
automatically and it cannot be disconnected. In this case, there must be no external ±12V
Baseboard mounted at
the bottom of the stack