
Philips Semiconductors
JTAG Functional Specification
PRODUCT SPECIFICATION
18-3
The JTAG instructions EXTEST, SAMPLE/PRELOAD,
and BYPASS are standard instructions and are not dis-
cussed here. The MACRO, BURNIN, and PASS_C_S in-
structions are used during hardware test mode, and are
also not discussed here. All other instructions are dis-
cussed in Section 18.3
18.3
USING JTAG FOR TM1300 DEBUG
Figure 18-2 shows an overview of the JTAG access path
from a host machine to a target TriMedia system and a
simplified block diagram of the TriMedia processor. The
JTAG Interface Module shown separately in the diagram
may be a PC add-on card such as PC-1149.1/100F
Boundary Scan Controller Board from Corelis Inc. or a
similar module connected to a PC serial or parallel port.
The JTAG interface module is necessary only for TriMe-
dia systems that are not plugged into a PC. For PC-host-
ed TriMedia systems, the host based debugger front-end
can communicate with the target resident debug monitor
via the PCI bus.
The enhancements to the standard functionality of JTAG
test logic provides a handshake mechanism for transfer-
ring data to and from a TriMedia processor’s MMIO reg-
isters reserved for this purpose, for posting an interrupt,
and for resetting processor state. The actual interpreta-
tion of the contents of the MMIO registers is determined
by a software protocol used by the debug monitor run-
ning on the TriMedia processor and the debug front-end
running on a host machine.
The communication between a host computer and a tar-
get TriMedia system via JTAG requires, at a high level of
abstraction, the following components.
A host computer with a serial or parallel inter-
face.
The host computer transfers data to and from the
JTAG interface module, preferably in word-parallel
fashion. A JTAG interface device driver is also
needed to access and modify the registers of the
JTAG interface module.
A JTAG interface module (hardware) that asyn-
chronously transfers data to and from the host
computer.
The interface module synchronously transfers data to
and from the JTAG TAP on a TriMedia processor, and
supplies the test clock, TCK, and other signals to the
TriMedia JTAG controller. The interface module may
be a PC plug-in board.
This module may transfer data from and to the host
computer in bit-serial or word-parallel fashion. It
transfers data from and to the JTAG registers on a
TriMedia processor in bit-serial fashion in accordance
with the IEEE 1149.1 standard. The JTAG interface
11110
MACRO
Hardware test mode select
01010
BURNIN
Private
01110
PASS_C_S
Private
Table 18-1. JTAG instruction encoding
Encoding
Instruction name
Action
Host Machine
JTAG Interface
JTAG board
Connector
Serial or Parallel
Connection
JTAG TAP (TCK, TMS, TDI, TDO)
Main
Memory
(SDRAM)
DSP
CPU
MMI
I$
D$
JTAG
controller
MMIO
Scan Chain connecting possibly
other chips on board
TriMedia Board
Figure 18-2. TriMedia system with JTAG test access
DATA Highway
Module
(such as a PC)
May be a PC plug-in board