Setting up the scan chain, Entering a trigger pattern, 4 setting up the scan chain – Achronix ACE Version 5.0 User Manual
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Running the SnapShot Debugger
Chapter 4. Tasks
The Automatically Detect Pod option is a convenience for when there is only one pod connected. If more
than one pod is automatically detected, the user must specify exactly which pod should be used.
The Specify Pod Name option allows the user to supply a comma-delimited list of one or more pod names
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.
ACE will then select the first available pod in the comma-delimited list; for example, an entry of ’usb12345,
net10234’ causes the software to first look for an available pod connected via USB with serial number 12345,
followed by a pod connected via Ethernet with serial number 10234.
Note:
Bitporter pod names consist of a three-letter suffix, ’usb’ for USB-connected pods, and ’net’ for
network-connected pods, followed by the a five-digit serial number. Network-connected pods can also
be specified via their IP address, for example, ’net192.168.1.100’.
For more information about Bitporter pod hardware and Bitporter pod naming, please refer to the Bitporter
User Guide (UG004).
Setting Up the Scan Chain
JTAG Scan chain details for the targeted device are specified under ”JTAG Scan Chain” in the
. The number of instruction register (IR) bits before the device is specified under ”IR Bits
Before Device”, while ”IR Bits After Device” specifies the number of IR bits that follow the target device in
the chain. ”Target Device Offset in Scan Chain” specifies the ordinal position relative to the beginning of the
scan chain.
In this configuration section, before refers to the more significant bits in the scan chain. After refers to the
less significant bits in the scan chain. Thus, in a chain of three SPD60 FPGAs (each SPD60 instruction register
consists of 23 bits, the total IR bits = 3×23 = 69 IR bits,) to specify the first device (IR scan chain bits [68:46])
requires an entry of 0:46:0 0 for ”IR Bits Before Device, 46 for ”IR Bits After Device”, and 0 for ”Target Device
Offset in Scan Chain”. The second SPD60 in a chain of three would be 23:23:1, and the third would be 46:0:2.
Example scan chain values for a series of three SPD60 devices in the same scan chain
Device (IR bit range within 69-bit IR scan chain)
IR Bits
Before
Device
IR Bits After
Device
Target
Device
Offset in
Scan Chain
1 (bits [68:46])
0
46
0
2 (bits [45:23])
23
23
1
3 (bits [22:0])
46
0
2
Specifying a single-device chain (where there’s nothing in the chain except the target device) requires an
entry of 0:0:0.
Entering a Trigger Pattern
The SnapShot Debugger is capable of handling 1-3 sequential trigger patterns. The post-trigger data is
sampled once the last trigger pattern in the sequence is matched. The user may specify the number of
desired sequential trigger patterns by clicking on the radio buttons to the left of each ”Trigger” in the
. If the radio button to the left of Trigger 1 is selected, Trigger 2 and Trigger 3
are ignored. If the radio button to the left of Trigger 2 is selected, Trigger 3 is ignored and SnapShot will
trigger when Trigger 1 is matched, followed (on any subsequent clock) by a match on Trigger 2. If the radio
button next to Trigger 3 is selected, then SnapShot will trigger after a match on Trigger 1, followed (on any
subsequent clock) by a match on Trigger2, followed (on any subsequent clock) by a match on Trigger3.
Each sequential trigger is hooked up to monitor channels 0-35 on the SnapShot Debugger core. The LSB of
the trigger pattern is hooked to monitor channel 0, and the MSB is hooked to monitor channel 35.
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specifying a single pod name is highly recommended
UG001 Rev. 5.0 - 5th December 2012
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