PLUS
ProASIC
Flash Family FPGAs
operation when no input data is supplied to them. These
pins are dedicated for boundary-scan test usage. Actel
recommends that a nominal 20 kΩ pull-up resistor is
added to TDO and TCK pins.
Boundary Scan (JTAG)
ProASICPLUS devices are compatible with IEEE Standard
1149.1, which defines a set of hardware architecture and
mechanisms for cost-effective, board-level testing. The
basic ProASICPLUS boundary-scan logic circuit is composed
of the TAP (test access port), TAP controller, test data
registers, and instruction register (Figure 1-12). This
circuit supports all mandatory IEEE 1149.1 instructions
(EXTEST, SAMPLE/PRELOAD and BYPASS) and the
optional IDCODE instruction (Table 1-6).
The TAP controller is a four-bit state machine (16 states)
that operates as shown in Figure 1-13 on page 1-12. The
’1’s and ‘0’s represent the values that must be present at
TMS at a rising edge of TCK for the given state transition
to occur. IR and DR indicate that the instruction register
or the data register is operating in that state.
ProASICPLUS devices have to be programmed at least
once for complete boundary-scan functionality to be
available. If boundary-scan functionality is required prior
to programming, refer to online technical support on the
Actel website and search for ProASICPLUS BSDL.
Each test section is accessed through the TAP, which has
five associated pins: TCK (test clock input), TDI and TDO
(test data input and output), TMS (test mode selector)
and TRST (test reset input). TMS, TDI and TRST are
equipped with pull-up resistors to ensure proper
I/O
I/O
I/O
I/O
I/O
Test Data
Registers
Bypass Register
Instruction
Register
TAP
Controller
Device
Logic
I/O
I/O
I/O
I/O
I/O
Figure 1-12 • ProASICPLUS JTAG Boundary Scan Test Logic Circuit
Table 1-6 • Boundary-Scan Opcodes
Hex Opcode
EXTEST
00
01
0F
05
FF
SAMPLE/PRELOAD
IDCODE
CLAMP
BYPASS
v5.2
1-11
ACTEL [ Actel Corporation ]
