Intel SA-1100 manual Reset, Pull-Up Resistors, Instruction Register, Public Instructions, 16-2

Boundary-Scan Test Interface

16.2Reset

The boundary-scan interface includes a state-machine controller (the TAP controller). In order to force the TAP controller into the correct state after power-up of the device, a reset pulse must be applied to the nTRST pin. If the boundary-scan interface is to be used, then nTRST must be driven low, and then high again. If the boundary-scan interface is not to be used, then the nTRST pin may be tied permanently low. Note that a clock on TCK is not necessary to reset the device.

The action of reset (either a pulse or a dc level) is as follows:

•System mode is selected (the boundary-scan chain does NOT intercept any of the signals passing between the pads and the core).

•IDcode mode is selected. If TCK is pulsed, the contents of the ID register will be clocked out of TDO.

16.3Pull-Up Resistors

The IEEE 1149.1 standard effectively requires that TDI, nTRST, and TMS should have internal pull-up resistors. To minimize static current draw, nTRST has an internal pull-down resistor. These pins can be left unconnected for normal operation and overdriven to use the JTAG features.

16.4Instruction Register

The instruction register is 5 bits in length. There is no parity bit. The fixed value loaded into the instruction register during the CAPTURE-IR controller state is: 00001.

16.5Public Instructions

The following public instructions are supported:

Instruction	Binary Code
EXTEST	00000
SAMPLE/PRELOAD	00001
CLAMP	00100
HIGHZ	00101
IDCODE	00110
BYPASS	11111
Private	00010, 00011, 00111, 01000-01111, 10000-11110

In the descriptions that follow, TDI and TMS are sampled on the rising edge of TCK, and all output transitions on TDO occur as a result of the falling edge of TCK.

16-2 SA-1100 Developer’s Manual