Figure 10.4 Diagram Of Output Cell; Figure 10.5 Diagram Of Bidirectional Cell - Renesas IDT 89HPES4T4 User Manual

Pci express switch

Table of Contents

IDT JTAG Boundary Scan

Notes

PES4T4 User Manual

Data from Core

Data from Previous Cell

shift_dr

The output enable cells are also output cells. The simplified logic is shown in Figure 10.5.

Output enable from core

Data from previous cell

clock_dr

shift_dr

Data from core

The bidirectional cells are composed of only two boundary scan cells. They contain one output enable

cell and one capture cell, which contains only one register. The input to this single register is selected via a

mux that is selected by the output enable cell when EXTEST is disabled. When the Output Enable Cell is

driving a high out to the pad (which enables the pad for output) and EXTEST is disabled, the Capture Cell

will be configured to capture output data from the core to the pad.

However, in the case where the Output Enable Cell is low (signifying a tri-state condition at the pad) or

EXTEST is enabled, the Capture Cell will capture input data from the pad to the core. The configuration is

shown graphically in Figure 10.5.

EXTEST

clock_dr

update_dr