MK50H25 STMICROELECTRONICS [STMicroelectronics], MK50H25 Datasheet - Page 37

• Manufacturer Part Number: MK50H25
• Description: HIGH SPEED LINK LEVEL CONTROLLER
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

4.3.1.4 Receive Message Descriptor 3 (RMD3)
4.3.2 Transmit Message Descriptor Entry
4.3.2.1 Transmit Message Descriptor 0 (TMD0)
BIT
15:00
BIT
15
14
13
12
NAME
MCNT
OWNA
OWNB
SLF
ELF
NAME
1
5
1
5
O
W
N
A
1
4
1
4
O
W
N
B
1
3
1
3
S
L
F
DESCRIPTION
Message Byte Count is the length, in bytes, of the received frame
MCNT is valid only when ELF is set to a one. MCNT is written by
MK50H25 and read by the Host. If ELF is set to a zero the entire
buffer has been utilized and the message byte count is given in
BCNT above. The value of this field is expressed in two’s comple-
ment. MCNT also reflects additional FCS bytes if FCSEN = 1.
DESCRIPTION
When this bit is a zero either the HOST or an I /O Acceleration Processor
owns this descriptor. When this bit is a one the MK50H25 owns this
descriptor. The host sets the OWNA bit after filling the buffer pointed
to by the descriptor entry. The MK50H25 releases the descriptor after
transmitting the buffer and receiving the proper acknowledgement
from the receiver. After the MK50H25, Host, or I/O Acceleration Proc-
essor has relinquished ownership of a buffer, it may not change any
field in the four words that comprise the descriptor entry.
This bit determines whether the HOST or an I /O Acceleration Processor
owns the buffer when OWNA is a zero. The MK50H25 never uses this
bit. This bit is provided to facilitate use of I/O Acceleration processors.
Start of Long Frame indicates that this is the first buffer used by the
MK50H25 for this frame. It is used for data chaining buffers. SLF is set
by the Host. When not chaining, SLF should be set to a one.
NOTE: A ”Long Frame” is any frame which needs data chaining.
End of Long Frame indicates that this is the last buffer used by the
MK50H25 for this frame. It is used for data chaining buffers. If both
SLF and ELF were set the frame would fit into one buffer and no
data chaining would be required. ELF is set by the Host. When not
chaining, ELF should be set to a one.
1
2
1
2
E
L
F
1
1
1
1
T
U
I
1
0
1
0
T
N
T
D
I
MCNT<15:00>
0
9
0
9
0
0
8
0
8
X
P
F
0
7
0
7
0
6
0
6
TBADR<23:16>
0
5
0
5
0
4
0
4
0
3
0
3
0
2
0
2
0
1
0
1
0
0
0
0
MK50H25
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