Datasheet

Figure 48-16. MLB DBR Directional Relationship
Rx
Data Buffer Ram
(DBR)
Tx
Host Bus
Interface
AMBA
MediaLB
Interface
Rx
Tx
HBI CAT RNW = 1
HBI CAT RNW = 0 MediaLB CAT RNW = 1
MediaLB CAT RNW = 0
Host
Controller
(
HC)
MediaLB
Bus
Channel Descriptor Table
The Channel Descriptor T
able (CDT) is comprised of 64 CTR entries (addresses 0x00–0x3F), as shown in Table
48-10.
Each 128-bit CDT entry (also referred to as a Channel Descriptor) is referenced by a Connection Label and contains
information about a data buffer in the DBR (e.g., buffer size, address pointers).
The format of each CDT entry (also referred to as a Channel Descriptor) depends on the channel type (e.g.
synchronous, isochronous, asynchronous, or control).
Note: All reserved Channel Descriptor bits must be written to ‘0’ by software when initialized.
Synchronous Channel Operation
The MLB provides two modes of operation (Standard and Multi-Frame per Sub- buffer) to provide flexibility for
implementing synchronous channels.
Channels set up for Standard mode require less buffer space, but have higher interrupt rates and more stringent
latency requirements. For channels configured for Standard mode, the Host Controller must transfer one full frame of
streaming data in/out of each streaming channel's data buffer for each frame period.
Channels set up for Multi-Frame per Sub-buffer mode require more buffer space, but have lower interrupt rates and
less stringent latency requirements. For channels configured for Multi-Frame per Sub-buffer mode, the Host
Controller must transfer N full frames of streaming data in/out of each streaming channel's data buffer for each frame
period.
To set up a channel in Multi-Frame per Sub-buffer mode:
• Program MLB_MLBC0.FCNT[2:0] to select the number of frames per sub-buffer
• Program the CAT to enable multi-frame sub-buffering (MFE = 1) for each particular channel
• Set the buffer depth in the CDT: BD = 4 × m × bpf - 1,
where m = frames per sub- buffer, bpf = bytes per frame
• Repeat for additional synchronous channels
A sample synchronous data buffer is shown in the following figure. Each data buffer contains four sub-buffers and
each sub-buffer contains space for 1 to 64 frames of data, determined by MLB_MLBC0.FCNT[2:0].
Figure 48-17. Synchronous Data Buffer Structure
Synchronous
Data Buffer
Sub-Buffer
0
Sub-Buffer
1
Sub-Buffer
2
Sub-Buffer
3
BA
BD
Synchronous Channel Descriptors
The format and field definitions for a synchronous CDT entry are shown in T
able 48-14 and Table 48-14, respectively.
Table 48-14. Synchronous CDT Entry Format
Bit Offset 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 WSBC Reserved
16 RSBC Reserved
SAM E70/S70/V70/V71 Family
Media Local Bus (MLB)
© 2019 Microchip T
echnology Inc.
Datasheet
DS60001527D-page 1353