
12-16
Lattice Semiconductor
LatticeECP/EC sysCONFIG Usage Guide
Table 12-4. LatticeECP/EC Device Preference List
Persistent
When using the sysCONFIG port to perform transparent readback the PERSISTENT preference must be set to
ON, this reserves the dual-purpose pins for configuration. PERSISTENT = ON prevents the user and the software
fitter from using any of the dual-purpose pins as general purpose I/O.
Configuration Mode
The device knows which physical port will be used by reading the highs and lows wired to the CFG[0:2] pins, how-
ever sometimes software needs to know the setting of the CFG pins as well. The Configuration Mode serves this
purpose. The fitter will be prevented from using the I/O pins associated with the selected Configuration Mode, how-
ever the user may assign these pins (a warning will be generated by the software). If the user requires these pins
as general purpose I/O they must adhere to the requirements listed above in the Configuration Pins section.
Normally, proper selection of the Configuration Mode is not strictly required. For pin reservation, for instance, the
user can place prohibits in the source code to insure that the fitter doesn’t use the configuration pins as general
purpose I/O. However, if multiple devices are being configured from one configuration device then the Configura-
tion Mode must match the CFG pins. This is required because the overflow option (Flow Through or Bypass) is
determined by the Configuration Mode (in software) and the CFG pins (in hardware). Note that if either overflow
option is selected, then the DONE_EX and WAKE_UP selections will be changed to correspond. See
Table 12-5for details on the Overflow Option defaults. For more information on the overflow options, see the Configuration
Options section of this document.
Table 12-5. Overflow Option Defaults
DONE Open Drain
The “DONE_OD” preference allows the user to configure the DONE pin as an open drain pin. The “DONE_OD”
preference is only used for the DONE pin. When the DONE pin is driven low, internally or externally, this indicates
that programming is not complete and the device is not ready for wake up. Once configuration is complete, with no
errors, and the device is ready for wake-up, the DONE pin must be driven high. For other devices to be used to con-
trol the wake-up process an open drain configuration is needed to avoid contention on the DONE pin. The
“DONE_OD” preference for the DONE pin defaults to ON. The DONE_OD preference will be automatically set to
the default if the DONE_EX preference is set to on. See
Table 12-6 for more information on the relationship
between DONE_OD and DONE_EX.
Preference (Preference)
Default Setting (All Settings)
PERSISTENT
ON [off, on]
CONFIG_MODE
DONE_OD
ON [on, off]
DONE_EX
OFF [off, on]
MCCLK_FREQ
Lowest Frequency (see device tables)
CONFIG_SECURE
OFF [off, on]
WAKE_UP
21 (DONE_EX = Off) [1:25] 4 (DONE_EX = On) [1:7]
COMPRESS_CONFIG
OFF (off, on)
Overflow Option
(Bypass, Flow Through)
DONE_EX Preference
WAKE_UP Preference
Off
Off (default)
Default 21 (user selectable 1 through 25)
Off
On
Default 21 (user selectable 1 through 25)
On
ON (automatically set by software)
Default 4 (user selectable 1 through 7)