
40
Lucent Technologies Inc.
Data Sheet
June 1999
ORCA Series 2 FPGAs
FPGA States of Operation
Prior to becoming operational, the FPGA goes through a 
sequence of states, including initialization, configuration, 
and start-up. Figure 36 outlines these three FPGA 
states.
5-4529(F).r6
Figure 36. FPGA States of Operation
Initialization
Upon powerup, the device goes through an initialization 
process. First, an internal power-on-reset circuit is trig-
gered when power is applied. When V
DD
 reaches the 
voltage at which portions of the FPGA begin to operate 
(2.5 V to 3 V for the OR2CxxA, 2.2 V to 2.7 V for the 
OR2TxxA/OR2TxxB), the I/Os are configured based on 
the configuration mode, as determined by the mode 
select inputs M[2:0]. A time-out delay is initiated when 
V
DD
 reaches between 3.0 V and 4.0 V (OR2CxxA) or 
2.7 V to 3.0 V (OR2TxxA/2TxxB) to allow the power 
supply voltage to stabilize. The INIT and DONE outputs 
are low. At powerup, if V
DD
 does not rise from 2.0 V to 
V
DD
 in less than 25 ms, the user should delay configu-
ration by inputting a low into INIT, PRGM, or RESET 
until V
DD
 is greater than the recommended minimum 
operating voltage (4.75 V for OR2CxxA commercial 
devices and 3.0 V for OR2TxxA/B devices). 
At the end of initialization, the default configuration 
option is that the configuration RAM is written to a low 
state. This prevents shorts prior to configuration. As a 
configuration option, after the first configuration (i.e., at 
reconfiguration), the user can reconfigure without 
clearing the internal configuration RAM first. 
The active-low, open-drain initialization signal INIT is 
released and must be pulled high by an external resis-
tor when initialization is complete. To synchronize the 
configuration of multiple FPGAs, one or more INIT pins 
should be wire-ANDed. If INIT is held low by one or 
more FPGAs or an external device, the FPGA remains 
in the initialization state. INIT can be used to signal that 
the FPGAs are not yet initialized. After INIT goes high 
for two internal clock cycles, the mode lines (M[3:0]) 
are sampled and the FPGA enters the configuration 
state.
The high during configuration (HDC), low during config-
uration (LDC), and DONE signals are active outputs in 
the FPGA’s initialization and configuration states. HDC, 
LDC, and DONE can be used to provide control of 
external logic signals such as reset, bus enable, or 
PROM enable during configuration. For parallel master 
configuration modes, these signals provide PROM 
enable control and allow the data pins to be shared 
with user logic signals.
If configuration has begun, an assertion of RESET or 
PRGM initiates an abort, returning the FPGA to the ini-
tialization state. The PRGM and RESET pins must be 
pulled back high before the FPGA will enter the config-
uration state. During the start-up and operating states, 
only the assertion of PRGM causes a reconfiguration.
In the master configuration modes, the FPGA is the 
source of configuration clock (CCLK). In this mode, the 
initialization state is extended to ensure that, in daisy-
chain operation, all daisy-chained slave devices are 
ready. Independent of differences in clock rates, master 
mode devices remain in the initialization state an addi-
tional six internal clock cycles after INIT goes high. 
When configuration is initiated, a counter in the FPGA 
is set to 0 and begins to count configuration clock 
cycles applied to the FPGA. As each configuration data 
frame is supplied to the FPGA, it is internally assem-
bled into data words. Each data word is loaded into the 
internal configuration memory. The configuration load-
ing process is complete when the internal length count 
equals the loaded length count in the length count field, 
and the required end of configuration frame is written. 
– ACTIVE I/O
– RELEASE INTERNAL RESET
– DONE GOES HIGH
START-UP
INITIALIZATION
CONFIGURATION
RESET
OR
PRGM
LOW
PRGM
LOW
– CLEAR CONFIGURATION MEMORY
– INIT LOW, HDC HIGH, LDC LOW
OPERATION
POWERUP
– POWER-ON TIME DELAY
– M[3:0] MODE IS SELECTED
– CONFIGURATION DATA FRAME WRITTEN
– INIT HIGH, HDC HIGH, LDC LOW
– DOUT ACTIVE
YES
NO
NO
RESET,
INIT,
OR
PRGM
LOW
BIT
ERROR
YES