User manual

Tasks and Kits
ProMaster 2500 User Manual 3-17
The value of
YYYY YYYY
is the address where the byte of data is stored
in the 2500’s RAM.
Relative Addressing
Under most circumstances the I/O Offset is left at its default value of
FFFFFFFF
. By default, the 2500 assumes that the first byte of data it
receives should be located at RAM address 0 and all other data bytes
received will be located in RAM at addresses relative to the address of the
first byte. During a data file download from the PC to the 2500, the
default value instructs the 2500 to take the first data byte in the file
(regardless of the address that byte has in the file) and save it at the 2500’s
RAM address = 0. The address of the first byte becomes the I/O Offset
value and is subtracted from all subsequent data file addresses to arrive
at the ultimate 2500 RAM address for that file data byte.
The sample below shows how this
relative
addressing works in a typical
application.
File Download:
File address number 800
– I/O offset number -800
---------------------------------- -----
XXXX XXXX
000
+
Begin RAM number +000
--------------------------------- -----
2500 RAM address =
YYYY YYYY
000
Absolute Addressing
This parameter is usually changed from the default during a file
download from the PC to 2500’s RAM. Some file formats (primarily the
Intel formats) use absolute addresses. In this context we mean that the
address of each data byte in the file is the absolute address and the data
byte associated with that address should be saved at the same address in
the 2500’s RAM. If your file uses absolute addressing, then the I/O Offset
should be set to 0.
The following example shows how this
absolute
addressing works in a
typical application.
File Download:
File address number 800
– I/O offset number – 000
---------------------------------- -------
XXXX XXXX 800
+
Begin RAM number + 000
---------------------------------- -------
2500 RAM address =
YYYY YYYY
800
If you have a file with absolute addressing and the programmer is using
the default (relative addressing), the file will download and the devices
will program without any error messages. However, the devices will not
be programmed correctly, because the RAM was not loaded with data at
the intended locations.