Chapter 9: Using User Flash Memory in MAX II Devices
9–7
UFM Functional Description
The undivided internal oscillator, which is not accessible, operates in a frequency
range from 13.33 to 22.22 MHz. The internal oscillator is enabled during power-up, in-
system programming, and real-time ISP. At all other times, the oscillator is not
running unless the UFM is instantiated in the design and the OSC_ENAport is
asserted. To see how specific operating modes of ALTUFMhandle OSC_ENA and the
oscillator, refer to “Software Support for UFM Block” on page 9–13. For user
generated logic interfacing to the UFM, the oscillator must be enabled during
PROGRAMor ERASEoperations, but not during READoperations. OSC_ENAcan be tied
low if you are not issuing any PROGRAMor ERASEcommands.
1
1
During real-time ISP operation, the internal oscillator automatically enables and
outputs through the OSCoutput port (if this port is instantiated) even though the
OSC_ENAsignal is tied low. You can use the RTP_BUSYsignal to detect the beginning
and ending of the real-time ISP operation for gated control of this self-enabled OSC
output condition.
The internal oscillator is not enabled all the time. The internal oscillator for the
program/eraseoperation is only activated when the flash memory block is being
programmed or erased. During the READoperation, the internal oscillator is activated
whenever the flash memory block is reading data.
Instantiating the Oscillator without the UFM
®
You can use the IO/MAX II oscillator megafunction selection in the MegaWizard
Plug-In Manager to instantiate the UFM oscillator if you intend to use this signal
without using the UFM memory block. Figure 9–4 shows the altufm_osc
megafunction instantiation in the Quartus II software.
Figure 9–4. The Quartus II altufm_osc Megafunction
®
This megafunction is in the I/O folder on page 2a of the MegaWizard Plug-In
Manager, as shown in Figure 9–5. You can start the MegaWizard Plug-In Manager on
the Tools menu.
© October 2008 Altera Corporation
MAX II Device Handbook
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