Table of Contents
Advertisement
12.2
JTAG-DP
12.2.1
The scan chain interface
ARM DDI 0337B
JTAG-DP contains a DP state machine (JTAG) that controls the JTAG-DP operation,
including controlling the scan chain interface that provides the external physical
interface to the JTAG-DP. It is based closely on the JTAG TAP State Machine, see IEEE
Std 1149.1-1990. This chapter describes both the JTAG-DP and its scan chain interface.
Figure 12-1 on page 12-4 shows an ARM Debug Interface with a JTAG-DP, including
the operation of the scan chain interface.
This section contains the following:
•
The scan chain interface
•
IR scan chain and IR instructions on page 12-7
•
DR scan chain and DR registers on page 12-10.
The JTAG-DP comprises:
•
a DP State Machine (JTAG)
•
an Instruction Register (IR) and associated IR scan chain, used to control the
behavior of the JTAG and the currently-selected data register
•
a number of Data Registers (DRs) and associated DR scan chains, that interface
to the registers in the JTAG-DP.
Physical connection to the JTAG-DP
Table 12-1 lists the JTAG-DP JTAG connections.
Copyright © 2005, 2006 ARM Limited. All rights reserved.
Table 12-1 JTAG-DP signal connections
Port
Direction
TDI
Input
TDO
Output
TCK
Input
TMS
Input
nTRST
Input
Debug Port
Description
Debug Data In
Debug Data Out
Debug Clock
Debug Mode Select
Debug Reset
12-3
Advertisement
Table of Contents
