Design Guide
Revision 1.12
1998-08-12
HMS F
IELDBUS
S
YSTEMS
AB
Page 12 (35)
4 Dual Ported RAM Interface
The easiest method to use the data transfer module is to integrate it into the system microprocessor bus.
This is achieved by using the DPRAM interface. Through this interface the handshaking protocol and the
access to all the relevant data is made.
4.1 Signal Description
The ANYBUS module is accessed through the application connector. This connector includes the power
supply, address and data bus and control signals for the DPRAM.
To achieve compatibility for future AnyBus products, please see chapter 3.1 before implementing.
For electrical characteristics, please see section 7 and Appendix C
4.2 Memory Map
After reset or power up of the DataTransfer module the following default memory mapping can be found.
The lowest 480 Bytes (000h - 1DFh) are dedicated to the input area and the following 480 Bytes (1E0h -
3BFh) are dedicated to the output area. The remaining 64 Bytes are divided into two 32 bytes areas. The
first area is used for fieldbus specific data and the last area is taken by different control registers.
The four different areas is mapped on the memory according the following:
Address
Name
Description
000h - 03Fh
Input data
(64 bytes)
Default no. of input bytes that can be addressed by all
supported fieldbus systems.
040h - 1DFh
Free
(416 bytes)
Area of free bytes that can be assigned to input data
1E0h - 21Fh
Output data
(64 bytes)
Default no. of output bytes that can be addressed by all
supported fieldbus systems.
220h - 3BFh
Free
(416 bytes)
Area of free bytes that can be assigned to output data
3C0h - 3DFh
Fieldbus specific data
(32 bytes)
3E0h - 3FFh
Control register
(32 bytes)
Using the input- and output- length register for I/O data (3F8h - 3Fbh) makes it possible to change the size
of the input and output area within the 480 supported bytes.
