
Data Sheet
June 1999
ORCA Series 2 FPGAs
56
Lucent Technologies Inc.
Special Function Blocks 
(continued) 
There are four ORCA-defined instructions. The PLC 
scan rings 1 and 2 (PSR1, PSR2) allow user-defined 
internal scan paths using the PLC latches/FFs. The 
RAM_Write Enable (RAM_W) instruction allows the 
user to serially configure the FPGA through TDI. The 
RAM_Read Enable (RAM_R) allows the user to read 
back RAM contents on TDO after configuration. 
ORCABoundary-Scan Circuitry
The ORCA Series boundary-scan circuitry includes a 
test access port controller (TAPC), instruction register 
(IR), boundary-scan register (BSR), and bypass regis-
ter. It also includes circuitry to support the four pre- 
defined instructions. 
Figure 49 shows a functional diagram of the boundary-
scan circuitry that is implemented in the ORCA series. 
The input pins’ (TMS, TCK, and TDI) locations vary 
depending on the part, and the output pin is the dedi-
cated TDO/RD_DATA output pad. Test data in (TDI) is 
the serial input data. Test mode select (TMS) controls 
the boundary-scan test access port controller (TAPC). 
Test clock (TCK) is the test clock on the board.
The BSR is a series connection of boundary-scan cells 
(BSCs) around the periphery of the IC. Each I/O pad on 
the FPGA, except for CCLK, DONE, and the boundary-
scan pins (TCK, TDI, TMS, and TDO), is included in 
the BSR. The first BSC in the BSR (connected to TDI) 
is located in the first PIC I/O pad on the left of the top 
side of the FPGA (PTA PIC). The BSR proceeds clock-
wise around the top, right, bottom, and left sides of the 
array. The last BSC in the BSR (connected to TDO) is 
located on the top of the left side of the array (PLA3). 
The bypass instruction uses a single FF which resyn-
chronizes test data that is not part of the current scan 
operation. In a bypass instruction, test data received on 
TDI is shifted out of the bypass register to TDO. Since 
the BSR (which requires a two FF delay for each pad) 
is bypassed, test throughput is increased when devices 
that are not part of a test operation are bypassed.
The boundary-scan logic is enabled before and during 
configuration. After configuration, a configuration 
option determines whether or not boundary-scan logic 
is used. 
The 32-bit boundary-scan identification register con-
tains the manufacturer’s ID number, unique part num-
ber, and version, but is not implemented in the ORCA 
series of FPGAs. If boundary scan is not used, TMS, 
TDI, and TCK become user I/Os, and TDO is 3-stated 
or used in the readback operation.
5-2840(C).r7
Figure 49. ORCA Series Boundary-Scan Circuitry Functional Diagram
TAP
CONTROLLER
BOUNDARY-SCAN REGISTER
PSR2 REGISTER (PLCs)
BYPASS REGISTER
DATA
MUX
INSTRUCTION DECODER
INSTRUCTION REGISTER
M
U
X
RESET
CLOCK-IR
SHIFT-IR
UPDATE-IR
PUR
TDO
SELECT
ENABLE
RESET
CLOCK-DR
SHIFT-DR
UPDATE-DR
TDI
DATA REGISTERS
PSR1 REGISTER (PLCs)
CONFIGURATION REGISTER
(RAM_R, RAM_W)
I/O BUFFERS
V
DD
TMS
V
DD
TCK
V
DD
PRGM
V
DD