13-17
Lattice Semiconductor
LatticeXP sysCONFIG Usage Guide
Table 13-9. Software Preference List for the LatticeXP
PERSISTENT Bit
In order to use the sysCONFIG port while in user mode to read SRAM or Flash memory, the PERSISTENT bit must
be set to ON. PERSISTENT = ON preserves all of the sysCONFIG pins so the FPGA can be accessed by an exter-
nal device at any time. PERSISTENT = ON lets the software know that all of the dual-purpose configuration pins
are reserved and NOT available for use by the fitter or the user. PERSISTENT = ON reserves all of the dual-pur-
pose sysCONFIG pins, without regard to CONFIG_MODE.
Configuration Mode
The device knows which physical sysCONFIG port will be used by reading the state of the CFG[1:0] pins, but the
fitter software also needs to know which port will be used. The fitter cannot sample the configuration pins so the
user must tell the fitter by selecting the proper CONFIG_MODE. CONFIG_MODE tells the fitter which sysCONFIG
pins are not available for use as user I/O.
There are several additional configuration options, such as overflow, that are set by software. These options are
selected by clicking Properties under Generate Bitstream Data in ispLEVER. If either overflow option is selected,
then the DONE_EX and WAKE_UP selections will be set to correspond (see
Table 13-10). Refer to the Configura-
tion Modes and Options section of this document for more details.
Table 13-10. 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 configuration is not complete and the device is not ready for the wake up sequence. Once configuration is com-
plete, with no errors, and the device is ready for wake up, the DONE pin must be driven high. For other devices to
be able to control 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 is automatically set to
ON if the DONE_EX preference is set to ON. See
Table 13-11 for more information on the relationship between
DONE_OD and DONE_EX.
DONE External
The LatticeXP device can wake up on its own after the Done bit is set or wait for the DONE pin to be driven high
externally. Set DONE_EX = ON to delay wake up until the DONE pin is driven high by an external signal synchro-
Preference Name
Default Setting [List of All Settings]
PERSISTENT
OFF [off, on]
CONFIG_MODE
NONE[SLAVE_PARALLEL, SLAVE_SERIAL, MASTER_SERIAL,
NONE]
DONE_OD
ON [off, on]
DONE_EX
OFF [off, on]
MCCLK_FREQ
CONFIG_SECURE
OFF [off, on]
WAKE_UP
21 (DONE_EX = off)
4 (DONE_EX = on)
PWRSAVE
OFF [off, on]
Overflow Option
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 (either)
On (automatically set by software)
Default 4 (User selectable 1 through 7)