
66
Lucent Technologies Inc.
Data Sheet
June 1999
ORCA Series 3C and 3T FPGAs
Microprocessor Interface (MPI)
(continued)
i960System
Figure 44 shows a schematic for connecting the ORCA
MPI
to supported i960 processors. In the figure, the
FPGA is shown as the only peripheral, with the FPGA
chip select lines,
CS0
and CS1, tied low and high,
respectively. The i960 address and data are multi-
plexed onto the same bus. This precludes memory
mapping of the FPGA in the i960memory space of a
multiperipheral system without some form of address
latching to capture and hold the address signals to
drive the
CS0
and/or CS1 signals. Multiple address sig-
nals could also be decoded and latched to drive the
CS0
and/or CS1 signals. If the
MPI
is not used for
FPGA configuration, decoding/latching logic can be
implemented internal or external to the FPGA. If logic
internal to the FPGA is used, the chip selects must be
routed out an output pin and then connected externally
to
CS0
and/or CS1. If the
MPI
is to be used for configu-
ration, any decode/latch logic used must be imple-
mented external to the FPGA since the FPGA logic has
not been configured yet.
5-5762(F)
Note: FPGA shown as only system peripheral with fixed-chip select
signals. For multiperipheral systems, address decoding and/
or latching can be used to implement chip selects.
Figure 44. i960MPI
The basic flow of a transaction on the i960/
MPI
inter-
face is given below. Pin descriptions are shown in
Table 17, and timing is shown in the ORCATiming
Characteristics section of this data sheet. For both read
and write transactions, the address latch enable (ALE)
is set up by the i960 at the FPGA to the falling edge of
the clock. The address, byte enables, chip selects, and
read/write (read low, write high) signals are normally
set up at the FPGA pins by the i960at the next rising
edge of the clock. At this same rising clock edge, the
i960asserts its address/data strobe (
ADS
) low. Data is
available to the
MPI
during a write at the rising clock
edge of the following clock cycle. The transfer is
acknowledged to the i960by the low assertion of the
ready/recover (
RDYRCV
) signal. The same process
applies to a read from the
MPI
except that the read
data is expected at the FPGA data pins by the i960at
the rising edge of the clock when
RDYRCV
is low. The
MPI
only drives
RDYRCV
low for one clock cycle.
Interrupts can be sent to the i960asynchronously to
the read/write process. Interrupt requests are sourced
by the user-logic in the FPGA. The
MPI
will assert the
request to the i960 as a direct interrupt signal and/or a
pollable bit in the
MPI
status register (discussed in the
MPI
Setup and Control section). The
MPI
will continue
to assert the interrupt request until the user-logic deas-
serts its interrupt request signal.
Table 17. i960/MPI Configuration
DOUT
CCLK
D[7:0]
MPI_CLK
MPI_RW
MPI_ACK
MPI_IRQ
MPI_ALE
MPI_STRB
MPI_BE1
HDC
LDC
TO DAISY-
CHAINED
DEVICES
ORCA
SERIES 3
8
FPGA
DONE
INIT
AD[7:0]
CLKIN
W/R
RDYRCV
XINTx
ALE
ADS
BE1
i960
CS1
CS0
i960SYSTEM CLOCK
V
DD
MPI_BE0
BE0
i960
Signal
ORCAPin
Name
MPI
I/O
Function
AD[7:0]
D[7:0]
I/O
Multiplexed 5-bit address/
8-bit data bus. The
address appears on D[4:0].
Address latch enable used
to capture address from
AD[4:0] on falling edge of
clock.
Address/data strobe to
indicate start of transac-
tion.
Active-low
MPI
select.
Active-high
MPI
select.
i960system clock. This
clock is sourced by the
system and not the i960
Write (high)/read (low)
signal.
Active-low ready/recover
signal indicating acknowl-
edgment of the transac-
tion.
Active-low interrupt
request signal.
ALE
RDY/RCLK/
MPI_ALE
I
ADS
RD
/
MPI_STRB
I
—
—
CS0
I
I
I
CS1
A7/
System
Clock
MPI_CLK
W/
R
A8/MPI_RW
I
RDYRCV
A9/
MPI_ACK
O
Any of
XINT
[7:0]
A11/
MPI_IRQ
O
BE0
A0/
MPI_BE0
I
Byte-enable 0 used as
address bit 0 in i9608-bit
mode.
Byte-enable 1 used as
address bit 1 in i9608-bit
mode.
BE1
A1/
MPI_BE1
I