Data Sheet
September, 2002
Lattice Semiconductor
45
ORCA Series 4 FPGAs
Special Function Blocks (continued)
The TAPC generates control signals that allow capture, shift, and update operations on the instruction and data
registers. In the capture operation, data is loaded into the register. In the shift operation, the captured data is
shifted out while new data is shifted in. In the update operation, either the instruction register is loaded for instruc-
tion decode, or the boundary-scan register is updated for control of outputs.
The test host generates a test by providing input into the ORCA Series TMS input synchronous with TCK. This
sequences the TAPC through states in order to perform the desired function on the instruction register or a data
register.
Figure 28 provides a diagram of the state transitions for the TAPC. The next state is determined by the
TMS input value.
5-5370(F)
Figure 28. TAP Controller State Transition Diagram
SELECT-
DR-SCAN
CAPTURE-DR
SHIFT-DR
EXIT1-DR
PAUSE-DR
EXIT2-DR
UPDATE-DR
1
0
10
RUN-TEST/
IDLE
1
TEST-LOGIC-
RESET
SELECT-
IR-SCAN
CAPTURE-IR
SHIFT-IR
EXIT1-IR
PAUSE-IR
EXIT2-IR
UPDATE-IR
1
0
10
00
0
1
0
1
0
1
0
1
11
0
Boundary-Scan Cells
Figure 29 is a diagram of the boundary-scan cell (BSC)
in the ORCA series PIOs. There are four BSCs in each
PIC: one for each pad, except as noted above. The
BSCs are connected serially to form the BSR. The BSC
controls the functionality of the in, out, and 3-state sig-
nals for each I/O pad.
The BSC allows the I/O to function in either the normal
or test mode. Normal mode is dened as when an out-
put buffer receives input from the PLC array and pro-
vides output at the pad or when an input buffer
provides input from the pad to the PLC array. In the test
mode, the BSC executes a boundary-scan operation,
such as shifting in scan data from an upstream BSC in
the BSR, providing test stimuli to the pad, capturing
test data at the pad, etc.
The primary functions of the BSC are shifting scan data
serially in the BSR and observing input (p_in), output
(p_out), and 3-state (p_ts) signals at the pads. The
BSC consists of three circuits: the bidirectional data
cell is used to access the input and output data, the
capture cell is used to capture the status of the I/O pad,
and the direction control cell is used to access the 3-
state value. All three cells consist of a FF used to shift
scan data which feeds a FF to control the I/O buffer.
The capture cell is connected serially to the bidirec-
tional data cell, which is connected serially to the direc-
tion control cell to form a boundary-scan shift register.
The TAPC signals (capture, update, shiftn, treset, and
TCK) and the MODE signal control the operation of the
BSC. The bidirectional data cell is also controlled by
the high out/low in (HOLI) signal generated by the
direction control cell. When HOLI is low, the bidirec-
tional data cell receives input buffer data into the BSC.
When HOLI is high, the BSC is loaded with functional
data from the PLC.