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68
Lattice Semiconductor
Data Sheet
November 2006
ORCA Series 3C and 3T FPGAs
Microprocessor Interface (MPI) (continued)
Status Register
The microprocessor interface status register is a read-only register, providing information to the host processor.
Table 22. Status Register
Conguration Data Register
The MPI conguration data register is a writable register in conguration mode and a readable register in readback
mode. For FPGA conguration, this is where the conguration data bytes are sequentially written by the host pro-
cessor. Similarly, for readback mode, the MPI provides the readback data bytes in this register for the host proces-
sor.
Readback Address Register 1
The MPI readback address register 1 is a writable register used to accept the least signicant address byte
(bits [7:0]) of the conguration data location to be read back.
Readback Address Register 2
The MPI readback address register 2 is a writable register used to accept the most signicant address byte
(bits [15:8]) of the conguration data location to be read back.
Bit #
Description
Bit 0
Reserved
.
Bit 1
Data Ready
. Set by the MPI, a 1 on this bit during conguration alerts the host processor that the FPGA
is ready for another byte of conguration data. During byte-wide readback, the MPI sets this bit to a 1 to
tell the host processor that a byte of conguration data is available for reading. This bit is cleared by a
host processor access (read or write) to the conguration data register.
Bit 2
IRQ
Pending
. The MPI sets this bit to 1 to indicate to the host processor that the FPGA has a pending
interrupt request. This bit may be used for the host processor to poll for interrupts if the MPI_IRQ pin out-
put of the FPGA has been masked at the host processor. This bit is set to 0 when the status register is
read. Interrupt requests from the FPGA user space must be cleared in FPGA user logic in addition to
reading this bit.
Bits
[4:3]
Bit Stream Error Flags
. Bits 3 and 4 are set by the MPI to indicate any error during FPGA congura-
tion. See bit 2 of control register 2 for the capability to alert the host processor of an error via the IRQ
signal during conguration. In the truth table below, bit 3 is the LSB (bit on right). These bits are cleared
to 0 when PRGM goes active:
00 = No error
01 = ID error
10 = Checksum error
11 = Stop-bit/alignment error
Bit 5
Reserved
.
Bit 6
INIT.
This bit reects the binary value of the FPGA INIT pin.
Bit 7
DONE
. This bit reects the binary value of the FPGA DONE pin.
Select
devices
have
been
discontinued.
See
Ordering
Information
section
for
product
status.