
Lucent Technologies Inc.
47
Data Sheet
June 1999
ORCA Series 2 FPGAs
Bit Stream Error Checking
There are three different types of bit stream error 
checking performed in the ORCA Series 2 FPGAs: 
ID frame, frame alignment, and parity checking.
An optional ID data frame can be sent to a specified 
address in the FPGA. This ID frame contains a unique 
code for the part it was generated for which is com-
pared within the FPGA. Any differences are flagged as 
an ID error. This frame is automatically created by the 
bit stream generation program in ORCAFoundry.
Every data frame in the FPGA begins with a start bit 
set to 0 and three or more stop bits set to 1. If any of 
the three previous bits were a 0 when a start bit is 
encountered, it is flagged as a frame alignment error.
Parity checking is also done on the FPGA for each 
frame, if it has been enabled by setting the prty_en bit 
to 1 in the ID frame. This is set by enabling the parity 
check option in the bit stream generation program of 
ORCA Foundry. Two parity bits, opar and epar, are 
used to check the parity of bits in alternating bit posi-
tions to even parity in each data frame. If an odd num-
ber of ones is found for either the even bits (starting 
with the start bit) or the odd bits (starting with the pro-
gram bit), then a parity error is flagged.
When any of the three possible errors occur, the FPGA 
is forced into the INIT state, forcing 
INIT
 low. The FPGA 
will remain in this state until either the 
RESET
 or 
PRGM
pins are asserted.
FPGA Configuration Modes
There are eight methods for configuring the FPGA. 
Seven of the configuration modes are selected on the 
M0, M1, and M2 inputs. The eighth configuration mode 
is accessed through the boundary-scan interface. A 
fourth input, M3, is used to select the frequency of the 
internal oscillator, which is the source for CCLK in 
some configuration modes. The nominal frequencies of 
the internal oscillator are 1.25 MHz and 10 MHz. The 
1.25 MHz frequency is selected when the M3 input is 
unconnected or driven to a high state. 
There are three basic FPGA configuration modes: 
master, slave, and peripheral. The configuration data 
can be transmitted to the FPGA serially or in parallel 
bytes. As a master, the FPGA provides the control sig-
nals out to strobe data in. As a slave device, a clock is 
generated externally and provided into CCLK. In the 
peripheral mode, the FPGA acts as a microprocessor 
peripheral. Table 10 lists the functions of the configura-
tion mode pins.
Table 10. Configuration Modes
Master Parallel Mode
The master parallel configuration mode is generally 
used to interface to industry-standard byte-wide mem-
ory, such as the 2764 and larger EPROMs. Figure 40 
provides the connections for master parallel mode. The 
FPGA outputs an 18-bit address on A[17:0] to memory 
and reads one byte of configuration data on the rising 
edge of RCLK. The parallel bytes are internally serial-
ized starting with the least significant bit, D0.
5-4483(F)
Figure 40. Master Parallel Configuration Schematic
There are two parallel master modes: master up and 
master down. In master up, the starting memory 
address is 00000 Hex and the FPGA increments the 
address for each byte loaded. In master down, the 
starting memory address is 3FFFF Hex and the FPGA 
decrements the address.
One master mode FPGA can interface to the memory 
and provide configuration data on DOUT to additional 
FPGAs in a daisy chain. The configuration data on 
DOUT is provided synchronously with the falling edge 
of CCLK. The frequency of the CCLK output is eight 
times that of RCLK.
M2
M1
M0
CCLK
Configuration 
Mode
Master 
Slave Parallel
Data
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
Output
Input
Reserved
Input
Output
Output
Output
Input
Serial
Parallel
Sync Peripheral
Master (up)
Async Peripheral
Master (down)
Slave
Parallel
Parallel
Parallel
Parallel
Serial
TO DAISY-
CHAINED
DEVICES
DOUT
CCLK
HDC
LDC
RCLK
A[17:0]
D[7:0]
DONE
PRGM
M2
M1
M0
A[17:0]
D[7:0]
OE
CE
PROGRAM
V
DD
V
DD
 OR GND
EPROM
ORCA
SERIES
FPGA