
SERIES AP48X ACROPACK
USER
’S MANUAL
Acromag, Inc. Tel: 248-295-0310
- 56 -
- 56 -
https://www.acromag.com
4.0 THEORY OF OPERATION
This section contains information regarding the hardware of the AP48X. A
description of the basic functionality of the circuitry used on the board is
also provided. Refer to the Figures 1 to 3 Block Diagrams for the AP48X
shown at the end of the manual as you review this material.
4.1 Counter Timer
Counter timer input control signals are TTL or RS422/RS485 logic level and
InA, InB, and InC are available via the field connector. See Table 2.1 to 2.3
for the list of these signals and their corresponding pin assignments.
Counter timer out signals OUT1 to 10 are TTL or RS422/RS485 logic level and
are available via the field I/O connector. See Table 2.1 to 2.3 for the output
signals and their corresponding pin assignments.
4.2 Digital Input/Output
Digital input/output signals to the FPGA are buffered using TTL drivers. Field
inputs to these buffers include a 4.7K pullup resistor to +3.3V. Output
operation is considered ‘Fail
-
safe’. That is, the Digital Input/Output signals
are always configured as input upon FPGA configuration during power-up.
This is done for safety reasons to ensure reliable control under all
conditions. Once configured the Digital Output channels will be set as
output signals.
4.3 Mini PCIe Interface
The Mini PCIe interface to the carrier board is made through 52-pin
connector (refer to Table 2.4). These connectors also p3.3V power
and JTAG signals to the module.
4.4 PCIe Interface Logic
The PCIe bus interface logic is embedded within the FPGA. This logic
includes support for PCIe commands, including: configuration read/write,
and memory read/write. In addition, the PCIe target interface uses a single
4K base address register, and implements target abort, retry, and
disconnect. The AP48X logic also implements interrupt requests via the PCIe
bus.
A FPGA device provides the control signals required to operate the board. It
decodes the selected addresses, control signals, and interrupt handling. It
also returns the acknowledgement messages required by the carrier/CPU
board per the PCIe specification. The program for the FGPA is stored in
separate Flash memory and loaded upon power-up.