DS785UM1
9-89
Copyright 2007 Cirrus Logic
1/10/100 Mbps Ethernet LAN Controller
EP93xx User’s Guide
9
9
9
The hard and soft threshold work in exactly the same
manner except one. The soft threshold will not cause a
bus request to be made if the bus is currently in use, but
only when it is deemed to be idle (no transfers for four
AHB clocks). The hard threshold takes effect immediately
regardless of the state of the bus. This operation allows for
more efficient use of the AHB bus by allowing smaller
transfers to take place when the bus is lightly loaded and
requesting larger transfers only when the bus is more
heavily loaded.
RXDThrshld
Address:
0x8001_00E0 - Read/Write
Suggested Value:
0x0004_0002
Chip Reset:
0x0000_0000
Soft Reset:
Unchanged
Definition:
Receive Descriptor Threshold register. The receive descriptor thresholds are
used to set a limit on the amount of empty space allowed in the MAC’s receive
descriptor FIFO before a bus request will be scheduled. When the number of
empty words in the FIFO exceeds the threshold value, the Descriptor
Processor will schedule a bus request to transfer descriptors. The actual
posting of the bus request may be delayed due to lack of resources in the
MAC, such as a RXDEnq equal to zero. The lower two bits of the thresholds
are always zero.
Bit Descriptions:
RSVD:
Reserved. Unknown During Read.
0:
Must be written as “0”.
RDHT:
Receive Status Hard Threshold.
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RSVD
RDHT
0
0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RSVD
RDST
0
0
Summary of Contents for EP93 Series
Page 28: ...P 6 DS785UM1 Copyright 2007 Cirrus Logic Preface EP93xx User s Guide PP P ...
Page 162: ...5 36 DS785UM1 Copyright 2007 Cirrus Logic System Controller EP93xx User s Guide 55 5 ...
Page 576: ...15 18 DS785UM1 Copyright 2007 Cirrus Logic UART2 EP93xx User s Guide 1515 15 ...
Page 634: ...17 38 DS785UM1 Copyright 2007 Cirrus Logic IrDA EP93xx User s Guide 1717 17 ...
Page 648: ...19 6 DS785UM1 Copyright 2007 Cirrus Logic Watchdog Timer EP93xx User s Guide 1919 19 ...
Page 688: ...21 32 DS785UM1 Copyright 2007 Cirrus Logic I2S Controller EP93xx User s Guide 2121 21 ...
Page 790: ...27 20 DS785UM1 Copyright 2007 Cirrus Logic IDE Interface EP93xx User s Guide 2727 27 ...
Page 808: ...28 18 DS785UM1 Copyright 2007 Cirrus Logic GPIO Interface EP93xx User s Guide 2828 28 ...