Microchip Technology megaAVR 0 Series Manual page 457

29.3.6 System Information Block
The System Information Block (SIB) can be read out at any time by setting the SIB bit in the KEY
instruction from
the debugger, which is vital in identifying and setting up the proper communication channel with the part.
The output of the SIB should be interpreted as ASCII symbols. The KEY size field should be set to 16
bytes when reading out the complete SIB, and an 8-byte size can be used to read out only the Family_ID.
See Figure 29-18
Figure 29-18. System Information Block Format
29.3.7 Enabling of KEY Protected Interfaces
Access to some internal interfaces and features are protected by the UPDI KEY mechanism. To activate
a KEY, the correct KEY data must be transmitted by using the KEY instruction as described in
instruction. Table 29-4
with the KEY active. There is no requirement when shifting in the KEY, but you would, for instance,
normally run a Chip Erase before enabling the NVMPROG KEY to unlock the device for debugging. But if
the NVMPROGKEY is shifted in first, it will not be reset by shifting in the Chip Erase KEY afterwards.
Table 29-4. KEY Activation Overview
KEY Name
Chip Erase
NVMPROG
USERROW-Write
Table 29-5 gives an overview of the available KEY signatures that must be shifted in to activate the
interfaces.
Table 29-5. KEY Activation Signatures
KEY Name
Chip Erase
NVMPROG
USERROW-Write
©
2018 Microchip Technology Inc.
KEY - Set Activation KEY. The SIB provides a compact form of providing information for
for SIB format description, and which data is available at different readout sizes.
16 8 [Byte][Bits]
[6:0] [55:0]
[7][7:0]
[10:8][23:0]
[13:11][23:0]
[14][7:0]
[15][7:0]
describes the available KEYs, and the condition required when doing the operation
Description
Start NVM Chip erase.
Clear Lockbits
Activate NVM
Programming
Program User Row on
Locked part
KEY Signature (LSB Written
First)
0x4E564D4572617365
0x4E564D50726F6720
0x4E564D5573267465
Unified Program and Debug Interface (UPDI)
Field Name
Family_ID
Reserved
NVM_VERSION
OCD_VERSION
RESERVED
DBG_OSC_FREQ
Requirements for
Operation
None
Lockbits Cleared.
ASI_SYS_STATUS.NVM
PROG set.
Lockbits Set.
ASI_SYS_STATUS.URO
WPROG set.
Datasheet Preliminary
®
megaAVR 0-Series
KEY
Reset
UPDI Disable/UPDI
Reset
Programming Done/
UPDI Reset
Write to KEY status bit/
UPDI Reset
Size
64 bits
64 bits
64 bits
DS40002015A-page 457