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MachXO2 Programming and Configuration Usage Guide
37
•
FLASH
– The Configuration Flash cannot be erased or programmed
•
FLASH_UFM
– The Configuration Flash and UFM cannot be erased or programmed
•
FLASH_UFM_SRAM
– The Configuration Flash, UFM, and SRAM cannot be erased or programmed
Once the ONE_TIME_PROGRAM preference is set for the Flash memory, the on-chip Flash memory cannot be
erased or programmed. The configuration data is prevented from further modification, but the SDM mode can still
be used to configure the device.
When the ONE_TIME_PROGRAM preference is set for the FLASH_UFM_SRAM memory, the device acts like an
ASIC. You are no longer able to reprogram the internal Flash or UFM, and the SRAM cannot be changed from the
JTAG port. Configuration of SRAM from on-chip Flash memory or external SPI Flash is still enabled.
Device Wake-up Sequence
When configuration is complete (the SRAM has been loaded), the device will wake up in a predictable fashion. If
the MachXO2 device is the only device in the chain, or the last device in a chain, the wake-up process should be
initiated by the completion of configuration. Once configuration is complete, the internal DONE bit will be set and
then the wake-up process will begin. Figure 18 shows the wake-up sequence using the internal clock.
Figure 18. Wake-up Sequence Using Internal Clock
Wake-up Signals
Three internal signals, GSR, GWDIS, and GOE, determine the wake-up sequence.
• When low, GOE prevents the device’s I/O buffers from driving the pins. The GOE only controls
output
pins. Once
the internal DONE is asserted the MachXO2 will respond to input data.
• GSR is used to set and reset the core of the device. GSR is asserted (low) during configuration and de-asserted
(high) in the wake-up sequence.
• When the GWDIS signal is low it safeguards the integrity of the RAM Blocks and LUTs in the device. This signal
is low before the device wakes up. This control signal does not control the primary input pin to the device but con-
trols specific control ports of EBR and LUTs.
• When high, the DONE pin indicates that configuration is complete and that no errors were detected.
MCLK
DONE BIT
GLOBAL OUTPUT ENABLE
GLOBAL SET/RESET
GLOBAL WRITE DISABLE
DONE PIN
T0
T1
T2
T3