Document Number: 002-00368 Rev. *K Page 96 of 153
However, the PPBL register can not be written by the WRAR command. Only the PPB Lock Bit Write (PLBWR) command can write
the PPBL register.
The command sequence and behavior is the same as the PP or 4PP command with only a single byte of data provided. See
Section 9.5.2, Page Program (PP 02h or 4PP 12h) on page 105.
The address map of the registers is the same as shown for Section 9.3.13, Read Any Register (RDAR 65h) on page 93.
9.3.15 Set Burst Length (SBL C0h)
The Set Burst Length (SBL) command is used to configure the Burst Wrap feature. Burst Wrap is used in conjunction with Quad I/O
Read and DDR Quad I/O Read, in legacy SPI or QPI Mode, to access a fixed length and alignment of data. Certain applications can
benefit from this feature by improving the overall system code execution performance. The Burst Wrap feature allows applications
that use cache, to start filling a cache line with instruction or data from a critical address first, then fill the remainder of the cache line
afterwards within a fixed length (8/16/32/64-bytes) of data, without issuing multiple read commands.
The Set Burst Length (SBL) command writes the CR4V register to enable or disable the wrapped read feature and set the wrap
boundary. When enabled the wrapped read feature changes the related read commands from sequentially reading until the
command ends, to reading sequentially wrapped within a group of bytes.
When CR4V[4] = 1, the wrap mode is not enabled and unlimited length sequential read is performed.
When CR4V[4] = 0, the wrap mode is enabled and a fixed length and aligned group of 8, 16, 32, or 64 bytes is read starting at the
byte address provided by the read command and wrapping around at the group alignment boundary.
The group of bytes is of length and aligned on an 8-, 16-, 32-, or 64-byte boundary. CR4V[1:0] selects the boundary. See
Configuration Register 4 Volatile (CR4V) on page 66.
The starting address of the read command selects the group of bytes and the first data returned is the addressed byte. Bytes are
then read sequentially until the end of the group boundary is reached. If the read continues the address wraps to the beginning of the
group and continues to read sequentially. This wrapped read sequence continues until the command is ended by CS# returning
high.
The Power-On Reset, hardware reset, or software reset default burst length can be changed by programming CR4NV with the
desired value using the WRAR command.
Table 60. Example Burst Wrap Sequences
CR4V[4,1:0]
Value (Hex)
Wrap
Boundary
(Bytes)
Start Address
(Hex) Address Sequence (Hex)
1X Sequential XXXXXX03 03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10, 11, 12, 13, 14, 15, 16, 17, 18, ...
00 8 XXXXXX00 00, 01, 02, 03, 04, 05, 06, 07, 00, 01, 02, ...
00 8 XXXXXX07 07, 00, 01, 02, 03, 04, 05, 06, 07, 00, 01, ...
01 16 XXXXXX02 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 00, 01, 02, 03, ...
01 16 XXXXXX0C 0C, 0D, 0E, 0F, 00, 01, 02, 03, 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, ...
02 32 XXXXXX0A 0A, 0B, 0C, 0D, 0E, 0F, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1A, 1B, 1C, 1D, 1E, 1F, 00, 01, 02,
03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, ...
02 32 XXXXXX1E 1E, 1F, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10, 11, 12, 13, 14, 15, 16,
17, 18, 19, 1A, 1B, 1C, 1D, 1E, 1F, 00, ...
03 64 XXXXXX03
03, 04, 05, 06, 07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1A, 1B,
1C, 1D, 1E, 1F, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 2A, 2B, 2C, 2D, 2E, 2F, 30, 31, 32, 33, 34,
35, 36, 37, 38, 39, 3A, 3B, 3C, 3D, 3E, 3F, 00, 01, 02 ...
03 64 XXXXXX2E
2E, 2F, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 3A, 3B, 3C, 3D, 3E, 3F, 00, 01, 02, 03, 04, 05, 06,
07, 08, 09, 0A, 0B, 0C, 0D, 0E, 0F, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 1A, 1B, 1C, 1D, 1E, 1F,
20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 2A, 2B, 2C, 2D, 2E, 2F, ...