User manual

Class 4
1149.1
Compliance
Class 0
Mscan,
Oscan 0-7
Jscan 2
BDX CDX
Pwr Ctl
JScan3
MultiDrop
ExtCmds
Delays
SScan 0-3
Jscan 0,1
Class 1
Class 2
Class 3
Class 5
cJTAG www.ti.com
5.2 cJTAG
This module implements IEEE 1149.7 compliant compact JTAG (cJTAG) adapter, which runs a 2-pin
communication protocol on top of a IEEE 1149.1 JTAG test access port (TAP). The 2-pin JTAG mode
using only TCK and TMS I/O pads is the default configuration after power up. The cJTAG configuration in
CC26xx implements a subset of class 4 feature scan modes. Class 4 inherits features from classes 0, 1,
2, and 3 (except the features mentioned in Table 5-3.) Figure 5-3 shows conceptual diagram of the cJTAG
module.
Figure 5-3. cJTAG Conceptual Diagram
• Class 0 – Strict compliance to IEEE 1149.1 specification with internal TAP selection
• Class 1 – Adds cJTAG command protocol, some optional discrete commands
• Class 2 – Adds serial select capability
• Class 3 – Adds JTAG star configuration, controller IDs and scan selection directives
• Class 4 – Adds advanced scan protocols
Table 5-2 lists the features in IEEE 1149.7 that are supported in CC26xx. The cJTAG module in the
CC26xx device supports 12 scan formats. The scan formats use a variety of compression protocols
ranging from 1 to 4 clocks per bit to serialize each packet.
Table 5-2. IEEE 1149.7 Feature Subset
Device Support Through
IEEE 1149.7 Feature Comment
cJTAG
Class 4 TAP Yes Supports 2-pin operation
Configuration
Data and custom channels for
Class 5 TAP No
background data transfer
FRST No Functional reset
TRST No Test reset
Optional components RDBK capability No Readback of register data
Aux pin functions Yes Reuse of TDI and TDO pins
TCKWID No Programmable TCK width
Power down logic capability for
Power control Power down logic No
cJTAG module
392
JTAG Interface SWCU117A–February 2015–Revised March 2015
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