AN57322
November 4, 2009 Document No. 001-57322 Rev. ** 7
9. Next, add a decision point (DP) state to loop through
this waveform until the GPIF transaction count
(GPIFTC) expires. To do this, test the internal
TCXpire flag in a DP state and only branch to the
IDLE state when the decision count expires. In the DP
state, increment the GPIFADR lines.
10. A DP must be implemented at the beginning of s1. To
do this, set an action point on the Status Trace by
clicking on the left boundary of s1.
11. A dialog box appears prompting you for DP branch
conditions. Select the condition as follows:
12. This sets the GPIF to look at only one signal, the
TCXpire flag. When the transaction count expires, the
GPIF sets the TCXpire flag to 1. To set the branch
condition, branch to the IDLE state and terminate the
waveform. Otherwise, loop back to S0 and continue
with the waveform. The transaction count decrements
with every “Activate Data” operation for FIFO Reads.
Note that this is different for FIFO Writes, which
specifically requires a “Next Data” event to decrement
the transaction count.
13. Next increment the GPIFADR lines. To do this, click
on the Addr trace at the left boundary of s1. The final
waveform should appear as follows:
14. Save your waveform by selecting File > Save.
This completes the read waveform. The write waveform is
modified while creating the read waveform. To change this
back, click the FIFO Write tab and put an action point on
data trace at the end state s1. This causes the data trace
to toggle HIGH. Right-click on the action point at the end
of s1 on the data trace and select De-activate Data.
Right-click the action point at the beginning of s1 and
select the Next FIFO data. This is done because data
action points located on the left edge of the IDLE state
cannot present any form of “Next Data”.
This completes the designing of GPIF waveforms. This
waveform can now be exported to a gpif.c file and
included in a project.
Exporting GPIF Waveforms
To export the waveforms to a C file and include it in the
firmware project, follow these steps:
1. Select Tools > Export to gpif.c File.
2. Save file as gpif.c in a temporary location.
uVision2 Project and Firmware
The next step is to create a project and write firmware to
interface the SRAM to the FX2LP device.
1. Create a new folder called SRAM_GPIF.
If you have already installed the EZ-USB FX2LP
development tools, create a new folder in the path
C:\Cypress\USB\Examples\FX2LP and name it
“SRAM_GPIF“
2. Copy the following project files from
C:\Cypress\USB\Examples\FX2LP\bulkloop to
the newly created folder.
dscr.a51
fw.c
bulkloop.c
3. Rename bulkloop.c as FX2_SRAM_GPIF.c.
4. Move the gpif.c file saved when exporting the GPIF
waveforms section to this directory.
5. Start Microvision (uv2). The project window appears
as follows.
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