
Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 24: TM3260 Debug
PNX15XX_SER_3
Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2006
24-4
(loaded in parallel into the shift register stage), n bits are shifted in and
simultaneously, n bits are shifted out. Finally the register is “updated” with the new n
bits shifted in.
Note that when a register is scanned, its old value is shifted out of TDO and the new
value shifted in via TDI is written to the register at the Update state. Hence, scan in/
out involve the same steps. This also means that reading a register via JTAG destroys
its contents unless otherwise stated.
Some registers are specied as read-only via JTAG so that when the controller
transitions to the Update state for the read-only register, the update has no effect.
Some times, read/write registers are needed (e.g., control registers used for
handshake) which must be read non-destructively. In such cases, the value shifted in
determines whether the old value is “remembered” or something else happens.
2.1.3
PNX15xx Series JTAG Instruction Set
PNX15xx Series uses a 5-bit JTAG instruction register. The unspecied opcodes are
private and their effects are undened.
Table 1 lists the JTAG instructions related to
TM_DBG module.
The standard JTAG instructions such as EXTEST, SAMPLE/PRELOAD, BYPASS and
IDCODE are implemented and listed in
Table 2.3.
Operation
3.1 Register Programming Guidelines
Because the JTAG data registers live in MMIO space and are accessible by both the
TM3260 CPU and the JTAG controller at the same time, race conditions must not
exist either in hardware or in software. The communication protocol uses a
handshake mechanism to avoid software race conditions.
Table 1: JTAG TM3260 Instruction Encoding
Encodin
g
Instruction name
Action
10001
TM_DBG_SEL_DATA_IN
Select TM_DBG_DATA_IN register
10010
TM_DBG_SEL_DATA_OUT
Select TM_DBG_DATA_OUT register
10011
TM_DBG_SEL_IFULL_IN
Select TM_DBG_IFULL_IN register
10100
TM_DBG_SEL_OFULL_OUT
Select TM_DBG_OFULL_OUT register
10101
TM_DBG_SEL_TM_DBG_CTL1
Select TM_DBG_CTRL register 1
10110
TM_DBG_SEL_TM_DBG_CTL2
Select TM_DBG_CTRL register 2
Table 2: JTAG Instruction Encoding
Encoding
Instruction Name
Action
00000
EXTEST
Select boundary scan register
00001
SAMPLE
Select boundary scan register
00010
ICODE
Select Identication register
11111
BYPASS
Select bypass register