AMD Geode LX 800@0.9W - Manual (Page 433)

AMD Geode™ LX Processors Data Book 433
Video Processor Register Descriptions 33234H
6.8.3.16 CRC Signature (CRC)
VP Memory Offset 088h
Type
R/W
Reset Value 00000000_00000000h
CRC Register Map
63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32
RSVD
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RSVD
SIGV
AL
SIGFR SIGEN
CRC Bit Descriptions
Bit Name Description
63:3 RSVD (RO) Reserved (Read Only). Reads back as 0.
2 SIGVAL (RO) Signature Valid (Read Only). If this bit is set, the signature operation has completed
and the signature may be safely read from the 32-Bit CRC Signature Register (VP Mem-
ory Offset 090h).
1 SIGFR Signature Free Run.
0: Disable. (Default). If this bit was previously set to 1, the signature process will stop at
the end of the current frame (i.e., at the next falling edge of VSYNC).
1: Enable. If SIGNEN (bit 0) is set to 1, the signature register captures data continuously
across multiple frames.
0 SIGEN Signature Enable.
0: Disable. The SIGVAL (bits [31:8]) is reset to 000001h in 24-bit mode or 000000h in 32-
bit mode and held (no capture). (Default)
1: Enable. When this bit is set to 1, the next falling edge of VSYNC is counted as the start
of the frame to be used for CRC checking with each pixel clock beginning with the next
VSYNC.
If SIGFR (bit 1) is set to 1, the signature register captures the pixel data signature con-
tinuously across multiple frames.
If SIGFR (bit 1) is cleared to 0, a signature is captured one frame at a time, starting
from the next falling VSYNC.
After a signature capture is complete, the SIGVAL (bit 2) can be read to determine the
CRC check status. In 32-bit CRC mode, the full 32-bit signature can be read from the 32-
Bit CRC Signature (VP Memory Offset 090h[31:0]). Then proceed to reset SIGEN, which
initializes SIGVAL as an essential preparation for the next round of CRC checks.