Datasheet

SN54LVTH18512, SN54LVTH182512, SN74LVTH18512, SN74LVTH182512
3.3-V ABT SCAN TEST DEVICES
WITH 18-BIT UNIVERSAL BUS TRANSCEIVERS
SCBS671B – AUGUST 1996 – REVISED OCTOBER 1997
12
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
instruction-register opcode description
The instruction-register opcodes are shown in Table 3. The following descriptions detail the operation of
each instruction.
Table 3. Instruction-Register Opcodes
BINARY CODE
†
BIT 7 → BIT 0
MSB → LSB
SCOPE OPCODE DESCRIPTION
SELECTED DATA
REGISTER
MODE
00000000 EXTEST Boundary scan Boundary scan Test
10000001 IDCODE Identification read Device identification Normal
10000010 SAMPLE/PRELOAD Sample boundary Boundary scan Normal
00000011 BYPASS
‡
Bypass scan Bypass Normal
10000100 BYPASS
‡
Bypass scan Bypass Normal
00000101 BYPASS
‡
Bypass scan Bypass Normal
00000110 HIGHZ Control boundary to high impedance Bypass Modified test
10000111 CLAMP Control boundary to 1/0 Bypass Test
10001000 BYPASS
‡
Bypass scan Bypass Normal
00001001 RUNT Boundary-run test Bypass Test
00001010 READBN Boundary read Boundary scan Normal
10001011 READBT Boundary read Boundary scan Test
00001100 CELLTST Boundary self test Boundary scan Normal
10001101 TOPHIP Boundary toggle outputs Bypass Test
10001110 SCANCN Boundary-control register scan Boundary control Normal
00001111 SCANCT Boundary-control register scan Boundary control Test
All others BYPASS Bypass scan Bypass Normal
†
Bit 7 is used to maintain even parity in the 8-bit instruction.
‡
The BYPASS instruction is executed in lieu of a SCOPE instruction that is not supported in the ’LVTH18512 or ’LVTH182512.
boundary scan
This instruction conforms to the IEEE Std 1149.1-1990 EXTEST instruction. The BSR is selected in the scan
path. Data appearing at the device input and I/O pins is captured in the associated BSCs. Data that has been
scanned into the I/O BSCs for pins in the output mode is applied to the device I/O pins. Data present at the device
pins, except for output enables, is passed through the BSCs to the normal on-chip logic. For I/O pins, the
operation of a pin as input or output is determined by the contents of the output-enable BSCs (bits 47–44 of the
BSR). When a given output enable is active (logic 0), the associated I/O pins operate in the output mode.
Otherwise, the I/O pins operate in the input mode. The device operates in the test mode.
identification read
This instruction conforms to the IEEE Std 1149.1-1990 IDCODE instruction. The IDR is selected in the scan
path. The device operates in the normal mode.
sample boundary
This instruction conforms to the IEEE Std 1149.1-1990 SAMPLE/PRELOAD instruction. The BSR is selected
in the scan path. Data appearing at the device input pins and I/O pins in the input mode is captured in the
associated BSCs, while data appearing at the outputs of the normal on-chip logic is captured in the BSCs
associated with I/O pins in the output mode. The device operates in the normal mode.