
54
Lucent Technologies Inc.
Data Sheet
June 1999
ORCA Series 2 FPGAs
Special Function Blocks 
(continued) 
Boundary Scan
The increasing complexity of integrated circuits (ICs) 
and IC packages has increased the difficulty of testing 
printed-circuit boards (PCBs). To address this testing 
problem, the IEEEstandard 1149.1 - 1990 (IEEEStan-
dard Test Access Port and Boundary-Scan Architec-
ture) is implemented in the ORCA series of FPGAs. It 
allows users to efficiently test the interconnection 
between integrated circuits on a PCB as well as test 
the integrated circuit itself. The IEEE1149.1 standard 
is a well-defined protocol that ensures interoperability 
among boundary-scan (BSCAN) equipped devices 
from different vendors. 
The IEEE1149.1 standard defines a test access port 
(TAP) that consists of a 4-pin interface with an optional 
reset pin for boundary-scan testing of integrated cir-
cuits in a system. The ORCA series FPGA provides 
four interface pins: test data in (TDI), test mode select 
(TMS), test clock (TCK), and test data out (TDO). The 
PRGM
 pin used to reconfigure the device also resets 
the boundary-scan logic.
The user test host serially loads test commands and 
test data into the FPGA through these pins to drive out-
puts and examine inputs. In the configuration shown in 
Figure 47, where boundary scan is used to test ICs, 
test data is transmitted serially into TDI of the first 
BSCAN device (U1), through TDO/TDI connections 
between BSCAN devices (U2 and U3), and out TDO of 
the last BSCAN device (U4). In this configuration, the 
TMS and TCK signals are routed to all boundary-scan 
ICs in parallel so that all boundary-scan components 
operate in the same state. In other configurations, mul-
tiple scan paths are used instead of a single ring. When 
multiple scan paths are used, each ring is indepen-
dently controlled by its own TMS and TCK signals. 
Figure 48 provides a system interface for components 
used in the boundary-scan testing of PCBs. The three 
major components shown are the test host, boundary- 
scan support circuit, and the devices under test 
(DUTs). The DUTs shown here are ORCA Series 
FPGAs with dedicated boundary-scan circuitry. The 
test host is normally one of the following: automatic test 
equipment (ATE), a workstation, a PC, or a micropro-
cessor. 
Fig.34.a(F).1C
 Key:
BSC = boundary-scan cell, BDC = bidirectional data cell, 
and DCC = data control cell.
Figure 47. Printed-Circuit Board with Boundary-
Scan Circuitry
The boundary-scan support circuit shown in Figure 48 
is the 497AA Boundary-Scan Master (BSM). The BSM 
off-loads tasks from the test host to increase test 
throughput. To interface between the test host and the 
DUTs, the BSM has a general microprocessor interface 
and provides parallel-to-serial/serial-to-parallel conver-
sion, as well as three 8K data buffers.
SCAN
OUT
TDI
TMS
TCK
TDO
U2
SEE ENLARGED VIEW BELOW
PLC
ARRAY
SCAN
IN
TDO TCK TMS TDI
TAPC
BYPASS
REGISTER
INSTRUCTION
REGISTER
BDC
BSC
P_IN
P_OUT
P_TS
SCAN
IN
PT[ij]
ENLARGED VIEW
TDI
TDO
TMS
TCK
U1
TDI
TDO
TMS
TCK
U4
TDI
TDO
TMS
TCK
U3
TDI
TDO
TMS
TCK
net a
net b
net c
s
DCC
SCAN
OUT
DCC
BSC
P_IN
P_OUT
P_TS
SCAN
IN
PB[ij]
BDC
SCAN
OUT
BDC
BSC
P_IN
P_OUT
P_TS
PR[ij]
DCC
SCAN
OUT
BSC
P_IN
P_OUT
P_TS
PL[ij]
SCAN
IN
DCC
BDC