Data Sheet
June 1999
ORCA Series 3C and 3T FPGAs
not used during the configuration process are
3-stated with internal pull-ups.
FPGA States of Operation (continued)
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.
Warning: During configuration, all OR3Txxx inputs
have internal pull-ups enabled. If these inputs are
driven to 5V, they will draw substantial current ( 5 ma).
This is due to the fact that the inputs are pulled up to
3V.
During configuration, the PIC and PLC latches/FFs are
held set/reset and the internal BIDI buffers are 3-
stated. The combinatorial logic begins to function as
the FPGA is configured. Figure 50 shows the general
waveform of the initialization, configuration, and start-
up states.
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.
Configuration
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.
The ORCA Series FPGA functionality is determined by
the state of internal configuration RAM. This configura-
tion RAM can be loaded in a number of different
modes. In these configuration modes, the FPGA can
act as a master or a slave of other devices in the sys-
tem. The decision as to which configuration mode to
use is a system design issue. Configuration is dis-
cussed in detail, including the configuration data format
and the configuration modes used to load the configu-
ration data in the FPGA, following a description of the
start-up state.
All OR3Cxx I/Os operate as TTL inputs during configu-
ration (OR3Txxx I/Os are CMOS-only). All I/Os that are
VDD
RESET
PRGM
INIT
M[3:0]
CCLK
HDC
LDC
DONE
USER I/O
INTERNAL
RESET
(gsrn)
INITIALIZATION
CONFIGURATION
START-UP
OPERATION
5-4482(F)
Figure 50. Initialization/Configuration/Start-Up Waveforms
86
Lucent Technologies Inc.
AGERE [ AGERE SYSTEMS ]
