User manual

Tasks and Kits
3-16 ProMaster 2500 User Manual
There is one situation when the word width value would be changed.
This occurs if you are trying to program 16-bit RAM data into two 8-bit
memory devices. Assume that the 2500 loads a file intended to program
16-bit data into two 8-bit devices. The low order bytes of each 16-bit word
are saved to all even address in RAM beginning with RAM address 0
(zero). The high order bytes for each word would be stored at RAM
address 1 and all odd address locations. If the default parameters are not
changed, the 2500 would program an 8-bit device (without any errors)
with both odd and even bytes. The device would not operate in a 16-bit
data circuit.
To program all low order bytes into one 8-bit device and all the high
order bytes into the second 8-bit device, the word width should be set as
if it were one “virtual” 16-bit device. The two 8-bit devices will operate in
their target circuit application “virtually” as if they were a single 16-bit
device.
To program a virtual 16-bit device using two 8-bit parts, perform the
following steps:
1. Create two Tasks, one for each 8-bit device that downloads the same
16-bit data file. In the first Task, Set Word Width = 16 (see Figure
3-11), and Set Begin RAM = 0 (default).
2. Create a second Task exactly the same as the first except: Set Begin
RAM = 1.
3. Load the first Task.
4. Program the number of devices required. The combination of these
two parameters instructs the 2500 to program the device from all
even RAM addresses, beginning with address 0. This creates the low
order device in the two-device set.
5. Load the second Task.
6. Program the number of devices equal to the number programmed by
the first Task. The 2500 programs the second device from all odd
RAM addresses, beginning with RAM address 1. This creates the
high order device in the two device set.
Setting I/O Offset
I/O Offset is a value that is subtracted from each file address during a
data file download from the PC to the 2500’s RAM. During a data file
upload from the 2500’s RAM to a PC file, the I/O Offset value is added to
the RAM address before it is transmitted.
The following example uses a file download, because it is the most
common application.
File Download:
File address number
– I/O offset number
----------------------------------
XXXX XXXX
+
Beginning RAM address number
-----------------------------------------------------
2500 RAM address =
YYYY YYYY