SAA2502 Datasheet, PDF (43/64 Pages) NXP Semiconductors – ISO/MPEG Audio Source Decoder

Philips Semiconductors
ISO/MPEG Audio Source Decoder
Preliminary specification
SAA2502
7.6.6.10 Ancillary data and program associated data
With standard MPEG input data, the last 54 bytes of each frame, which may carry Ancillary Data (AD), are buffered by
the SAA2502 to be read by the host. Subsequent ancillary data bytes are read in reversed order with respect to their
order in the input data bit stream; the first item data byte is the last frame byte in the input bit stream. The ancillary data
block of local registers is refilled for every frame. The host must either know or determine itself how many of the ancillary
data bytes are valid per frame. The ancillary data block contains only valid data when status flag INSYNC is set.
Table 52 Ancillary data: 54 bytes (read-only, restricted block type, local address = 25H)
SUBSEQUENT BYTES
7
6
5
4
3
2
1
0
AD byte 1 to byte 54
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
Similarly when scale factor CRCs are enabled, the Fixed Program Associated Data (FPAD) and extended Program
Associated Data (XPAD) bytes contained in each frame may be read, with the 2 FPAD bytes first, followed by maximum
52 XPAD bytes. Subsequent FPAD and XPAD bytes are read in reversed order with respect to their order in the input
data bit stream; the first item data byte is the last PAD byte in the input bit stream. The host must determine itself how
many of the XPAD bytes are valid per frame by interpretation of the FPAD content. The PAD data block contains only
valid data when status flag INSYNC is set.
Table 53 XPAD plus FPAD: 54 bytes (read-only, restricted block type, local address = 25H)
SUBSEQUENT BYTES
7
6
5
4
3
2
1
0
FPAD bytes 1 and 2;
bit 7
bit 6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
XPAD byte 1 to byte 52
7.6.6.11 Continue block operation
Local address 00H is reserved for continuation of restricted type block operations. Whenever this local address is used,
it will result in continuation of any restricted type block transfer at the point where it was interrupted (provided that no
other restricted type SAA2502 transfer was carried out since).
1997 Nov 17
43