scan_dr_hw_jtag - 2020.2 English - UG835

Vivado Design Suite Tcl Command Reference Guide (UG835)
Document ID
UG835
Release Date
2020-11-18
Version
2020.2 English

Perform shift DR on 'hw_jtag'.

Syntax

scan_dr_hw_jtag [‑tdi <arg>] [‑tdo <arg>] [‑mask <arg>] [‑smask <arg>]
    [‑quiet] [‑verbose] <length>

Returns

hardware TDO

Usage

Name Description
[-tdi] Hex value to be scanned into the target
[-tdo] Hex value to be compared against the scanned value
[-mask] Hex value mask applied when comparing TDO values
[-smask] Hex value mask applied to TDI value
[-quiet] Ignore command errors
[-verbose] Suspend message limits during command execution
<length> Number of bits to be scanned.

Categories

Hardware, Object

Description

The scan_dr_hw_jtag command specifies a scan pattern to be scanned into the JTAG interface target data register.

The command targets a hw_jtag object which is created when the hw_target is opened in JTAG mode through the use of the open_hw_target -jtag_mode command.

When targeting the hw_jtag object prior to shifting the scan pattern specified in the scan_dr_hw_jtag command, the last defined header property (HDR) will be pre-pended to the beginning of the specified data pattern, and the last defined trailer property (TDR) will be appended to the end of the data pattern.

The options can be specified in any order, but can only be specified once. The number of bits represented by the hex strings specified for -tdi, -tdo, -mask, or -smask cannot be greater than the maximum specified by <length>. Leading zeros are assumed for a hex string if the number of bits represented by the hex strings specified is less than the <length>.

When shifting the data bits to the target data register, the scan_dr_hw_jtag command moves the JTAG TAP from the current stable state to the DRSHIFT state according to the state transition table below: 
Current State     Transitions to get to DRSHIFT state                    
RESET             IDLE -> DRSELECT -> DRCAPTURE -> DRSHIFT                 
IDLE              DRSELECT -> DRCAPTURE -> DRSHIFT                              
IRPAUSE           IREXIT2 -> IRUPDATE -> DRSELECT -> DRCAPTURE -> DRSHIFT    
DRPAUSE           DREXIT2 -> DRSHIFT                                           
DRPAUSE*          DREXIT2 -> DRUPDATE -> DRSELECT -> DRCAPTURE -> DRSHIFT
Note: * With -force_update option set.

After the last data bit is shifted into the target data register, the scan_dr_hw_jtag command moves the JTAG TAP to the IDLE state, or to the stable state defined by the run_state_hw_jtag command.

The scan_dr_hw_jtag command returns a hex array containing captured TDO data from the hw_jtag, or returns an error if it fails.

The command raises an error that can be trapped by the Tcl catch command if TDO data from the hw_jtag does not match specified -tdo argument.
Tip: If -tdo and -mask arguments are specified, then the mask is applied to the -tdo option and the hw_jtag TDO data returned before comparing the two.

Arguments

-tdi <arg> - (Optional) The value to be scanned into the target, expressed as a hex value. If this option is not specified, the -tdi value from the last scan_dr_hw_jtag command will be used. The -tdi option must be explicitly specified for the first scan_dr_hw_jtag command, and when the <length> changes.

-tdo <arg> - (Optional) Specifies the data value, expressed as a hex string, to be compared against the actual TDO value scanned out of the hw_jtag data register. If this option is not specified no comparison will be performed. If the -tdo option is not specified, the -mask option will be ignored.

-mask <arg> - (Optional) The mask to use when comparing -tdo value against the actual TDO value scanned out of the hw_jtag. A '1' in a specific bit position indicates the bit value should be compared. A '0' indicates the value should not be used for comparison. If -mask is not specified, the -mask value from the last scan_dr_hw_jtag command will be used.
Important: If the <length> changes and the -mask option is not specified, the -mask pattern used is all '1's.
-smask <arg> - (Optional) The mask to use with -tdi data. A '1' in a specific bit position indicates the TDI data in that bit position is significant; a '0' indicates it is not. The -smask option will be applied even if the -tdi option is not specified. If -smask is not specified, the -smask value from the last scan_dr_hw_jtag command will be used.
Important: If the <length> changes and the -smask option is not specified, the -smask pattern used is all '1's.
-quiet - (Optional) Execute the command quietly, returning no messages from the command. The command also returns TCL_OK regardless of any errors encountered during execution.
Note: Any errors encountered on the command-line, while launching the command, will be returned. Only errors occurring inside the command will be trapped.
-verbose - (Optional) Temporarily override any message limits and return all messages from this command.
Note: Message limits can be defined with the set_msg_config command.

<length> - (Required) A 32-bit unsigned decimal integer greater than 0, specifying the number of bits to be scanned from the data register.

Example

The following example scans the JTAG data register for a 24 bit value: 
scan_dr_hw_jtag  24
The following example sends a 24 bit value 0x00_0010 (LSB first) to TDI, then captures the data output, TDO, applies a mask with 0xF3_FFFF, and compares the returned TDO value against the specified value -tdo 0x81_8181: 
scan_dr_hw_jtag  24 -tdi 000010 -tdo 818181 -mask F3FFFF -smask 0
This example pads the specified TDI value 0x3f with leading 0x: 
scan_dr_hw_jtag 24 -tdi 3f
To break up a long data register shift into multiple SDR shifts, specify an end_state of DRPAUSE. This will cause the first scan_dr_hw_jtag command to end in the DRPAUSE stable state, and then the subsequent scan_dr_hw_jtag commands will go to DREXIT2 state before going back to DRSHIFT. 
run_state_hw_jtag DRPAUSE    
scan_dr_hw_jtag 16 -tdi aabb    
scan_dr_hw_jtag 16 -tdi ccdd    
scan_dr_hw_jtag 16 -tdi ceff    
scan_ir_hw_jtag 6 -tdi 05

See Also