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SN54BCT8244A, SN74BCT8244A
SCAN TEST DEVICES
WITH OCTAL BUFFERS
SCBS042E FEBRUARY 1990 REVISED JULY 1996
10
POST OFFICE BOX 655303
DALLAS, TEXAS 75265
POST OFFICE BOX 1443
HOUSTON, TEXAS 772511443
instruction-register opcode description
The instruction-register opcodes are shown in Table 2. The following descriptions detail the operation of
each instruction.
Table 2. Instruction-Register Opcodes
BINARY CODE
BIT 7
→ BIT 0
MSB
→ LSB
SCOPE OPCODE
DESCRIPTION
SELECTED DATA
REGISTER
MODE
X0000000
EXTEST/INTEST
Boundary scan
Test
X0000001
BYPASS
Bypass scan
Bypass
Normal
X0000010
SAMPLE/PRELOAD
Sample boundary
Boundary scan
Normal
X0000011
INTEST/EXTEST
Boundary scan
Test
X0000100
BYPASS
Bypass scan
Bypass
Normal
X0000101
BYPASS
Bypass scan
Bypass
Normal
X0000110
HIGHZ (TRIBYP)
Control boundary to high impedance
Bypass
Modified test
X0000111
CLAMP (SETBYP)
Control boundary to 1/0
Bypass
Test
X0001000
BYPASS
Bypass scan
Bypass
Normal
X0001001
RUNT
Boundary run test
Bypass
Test
X0001010
READBN
Boundary read
Boundary scan
Normal
X0001011
READBT
Boundary read
Boundary scan
Test
X0001100
CELLTST
Boundary self test
Boundary scan
Normal
X0001101
TOPHIP
Boundary toggle outputs
Bypass
Test
X0001110
SCANCN
Boundary-control register scan
Boundary control
Normal
X0001111
SCANCT
Boundary-control register scan
Boundary control
Test
All others
BYPASS
Bypass scan
Bypass
Normal
Bit 7 is a don’t-care bit; X = don’t care.
The BYPASS instruction is executed in lieu of a SCOPE
instruction that is not supported in the ’BCT8244A.
boundary scan
This instruction conforms to the IEEE Standard 1149.1-1990 EXTEST and INTEST instructions. The BSR is
selected in the scan path. Data appearing at the device input terminals is captured in the input BSCs, while data
appearing at the outputs of the normal on-chip logic is captured in the output BSCs. Data that has been scanned
into the input BSCs is applied to the inputs of the normal on-chip logic, while data that has been scanned into
the output BSCs is applied to the device output terminals. The device operates in the test mode.
bypass scan
This instruction conforms to the IEEE Standard 1149.1-1990 BYPASS instruction. The bypass register is
selected in the scan path. A logic 0 value is captured in the bypass register during Capture-DR. The device
operates in the normal mode.
sample boundary
This instruction conforms to the IEEE Standard 1149.1-1990 SAMPLE/PRELOAD instruction. The BSR is
selected in the scan path. Data appearing at the device input terminals is captured in the input BSCs, while data
appearing at the outputs of the normal on-chip logic is captured in the output BSCs. The device operates in the
normal mode.