Datasheet

230
ATtiny828 [DATASHEET]
8371A–AVR–08/12
See “Boot Loader Lock Bits” on page 218 for how different settings of the boot loader lock bits affect Flash access.
22.4.2 Fuse Bit Read
The algorithm for reading fuse bytes is similar to the one described above for reading lock bits, only the addresses are
different.
To read the Fuse Low Byte (FLB), follow the below procedure:
1. Load the Z-pointer with 0x0000.
2. Set RWFLB and SPMEN bits in SPMCSR.
3. Issue an LPM instruction within three clock cycles.
4. Read the FLB from the LPM destination register.
If successful, the contents of the destination register are as follows.
For a detailed description and mapping of the Fuse Low Byte, see Table 91 on page 227.
To read the Fuse High Byte (FHB), replace the address in the Z-pointer with 0x0003 and repeat the procedure above. If
successful, the contents of the destination register are as follows.
For a detailed description and mapping of the Fuse High Byte, see Table 90 on page 227.
To read the Fuse Extended Byte (FEB), replace the address in the Z-pointer with 0x0002 and repeat the previous
procedure. If successful, the contents of the destination register are as follows.
For a detailed description and mapping of the Fuse Extended Byte, see Table 89 on page 226.
22.4.3 Device Signature Imprint Table Read
To read the contents of the device signature imprint table, follow the below procedure:
1. Load the Z-pointer with the table index.
2. Set RSIG and SPMEN bits in SPMCSR.
3. Issue an LPM instruction within three clock cycles.
4. Read table data from the LPM destination register.
If successful, the contents of the destination register are as described in section “Device Signature Imprint Table” on
page 228.
Bit 76543210
Rd FLB7 FLB6 FLB5 FLB4 FLB3 FLB2 FLB1 FLB0
Bit 76543210
Rd FHB7 FHB6 FHB5 FHB4 FHB3 FHB2 FHB1 FHB0
Bit 76543210
Rd FEB7 FEB6 FEB5 FEB4 FEB3 FEB2 FEB1 FEB0