ACC-72EX User Manual
Theory of Operation
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THEORY OF OPERATION
The ACC-72EX board is organized as a motherboard/daughter board system. The motherboard contains
the UBUS interface, diagnostics, and the fieldbus connections. The daughter board contains the
intelligence (firmware which will be referred as netX) and the interface electronics required for each
fieldbus. There is a different daughter board for each fieldbus.
The netX firmware on the daughter board implements each fieldbus communications protocol. Fieldbus
data is transferred to/from the fieldbus and placed in a Dual-Ported RAM (memory) on the daughter
board. The structure of this DPRAM is given later in this manual and is common for all the field buses.
ACC-72EX supports up to 64K DPRAM on each device (one full chip-select width).
The PMAC side of the DPRAM is interfaced to the UBUS. PMAC programs access the fieldbus data by
reading or writing data to memory addresses corresponding to the location of the PMAC Gateway 3U
board’s DPRAM.
UBUS Interface
The UBUS is Delta Tau’s bus interface for the UMAC controller. The ACC-72EX maps to the UBUS as
a DPRAM style board. It occupies contiguous memory locations (both X and Y memory for Turbo
PMAC) of the lower two bytes of the 24-bit (middle 16 bits of each 32 bit word for Power PMAC),
DPRAM addresses. Because the DPRAM size supported on ACC-72EX can be as large as 64K, each card
will occupy one full Chip Select addressing space. There can be a maximum of two ACC-72EX cards per
Turbo/Power UMAC (cannot be in a MACRO Station).
M-Variables can be mapped to these locations to move data to and from the fieldbus and PMAC. In
addition to fieldbus data, there is a block of memory that indicates the ACC-72EX’s status.
How ACC-72EX Works
1.
The ACC-72EX organizes fieldbus bytes in dual-port memory on the COMX module. These fieldbus
bytes are mapped into PMAC’s memory space via the UBUS interface.
2.
PMAC M-Variables are used to move data to and from the fieldbus or to control the COMX board.
3.
An E-point jumper on the ACC-72EX sets the address of the board in PMAC memory space.
4.
The COMX board is configurable via a USB port. SYCON.NET is provided with the COMX board
for this purpose.
5.
Diagnostic LEDs are provided for a visual indication of board status.
