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Lattice Semiconductor
67
Data Sheet
November 2006
ORCA Series 3C and 3T FPGAs
Microprocessor Interface (MPI) (continued)
Scratchpad Register
The MPI scratchpad register is an 8-bit read/write register with no dened operation. It may be used for any user-
dened function.
Control Register 2
The MPI control register 2 is a read/write register. The host processor writes a control byte to congure the MPI. It
is readable by the host processor to verify the status of control bits it had previously written.
Table 21. MPI Control Register 2
Bit #
Bit Name
Description
Bit 0
EN_IRQ_CFG
Enable IRQ for Configuration Data Request in Daisy-Chain Configuration
Mode
. Setting this bit to a 1 prior to conguration enables the IRQ signal to go active
when new data is requested for conguration writes or is available for conguration
reads to/from the conguration data register. A 0 clears the IRQ enable. This bit is
only valid for daisy-chain conguration. Default = 0.
Bit 1
EN_IRQ_ERR
Enable IRQ for Bit Stream Error
. Setting this bit to a 1 prior to conguration
enables the IRQ signal to go active on the occurrence of a bit stream error during
conguration. A 0 clears the IRQ enable. This bit only has effect while in congura-
tion mode. Default = 0.
Bit 2
EN_IRQ_USR
Enable IRQ from the User FPGA Space
. Setting this bit to a 1 allows user-dened
circuitry in the FPGA to generate an interrupt to the host processor by sourcing a
logic low on the UIRQ signal in the user logic. Default = 0.
Bit 3
MP_DAISY
MPI
Daisy-Chain Output Enable
. Setting this bit to a 1 enables daisy-chain output
of the conguration data. See the Conguration section of this data sheet for daisy-
chain conguration details. Default = 0.
Bit 4
MP_HOLD_BUS Enable Bus Holding During Daisy-Chain Configuration Mode. Setting this bit to
a 1 will cause the MPI to wait until the FPGA conguration logic has serialized a
byte of conguration data before acknowledging the transaction. The data is only
serialized if the MP_DAISY (bit 3 above) control bit is set to 1. If MP_HOLD_BUS is
set to 0, the MPI will immediately acknowledge a conguration data byte transfer.
Immediate acknowledgment allows the host processor to perform other tasks during
FPGA conguration by polling the MPI status register (or by interrupt) and only write
conguration data when the FPGA is ready. Default = 0.
Bit 5
MP_USER
MPI
User Mode Enable
. Setting this bit to a 1 will enable the MPI for user mode
operation. MP_USER must be set prior to the FPGA DONE signal going high during
conguration. The MPI may also be enabled for user operation via the conguration
bit stream. Default = 0.
Bit 6
Reserved
—
Bit 7
Reserved
—
Select
devices
have
been
discontinued.
See
Ordering
Information
section
for
product
status.