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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
151
The following table specifies the relationship between
this bit and the corresponding Handshaking Mode.
Note:
1. The Handshaking Mode selection applies to both the
Transmit UTOPIA Interface and Receive UTOPIA
Interface blocks.
2. Since Multi-PHY mode operation requires the use
of “Cell-Level” Handshaking, this bit-field is ignored
if the UNI is operating in the Multi-PHY mode.
3. Finally, the UNI will be operating in the “Cell-Level”
Handshaking Mode upon power up or reset.
Therefore, the user must write a “0” to this bit-field
in order to configure the UNI into the “Octet Level
Handshaking” mode.
Figure 34 presents a timing diagram that illustrates
the behavior of various Transmit UTOPIA Interface
block signals, when the Transmit UTOPIA Interface
block is operating in the “Cell-Level” Handshaking
Mode.
Note:
regarding Figure 34
1. The Transmit UTOPIA Data Bus is configured to be
16 bits wide. Hence, the data which the ATM Layer
processor places on the Transmit UTOPIA Data
Bus is expressed in terms of 16-bit words: W0–W26.
2. The Transmit UTOPIA Interface Block is configured
to handle 54 bytes/cell. Hence, Figure 34 illustrates
the ATM Layer processor writing 27 words (W0
through W26) for each ATM cell.
UTOPIA Configuration Register: Address = 6Ah
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Unused
Handshake Mode
M-PHY
CellOf52 Bytes
TFIFODepth[1, 0]
UtWidth16
RO
R/W
R/W
R/W
R/W
R/W
T
ABLE
13: T
HE
R
ELATIONSHIP
BETWEEN
THE
CONTENTS
IN
BIT
FIELD
5 (H
ANDSHAKE
M
ODE
)
WITHIN
THE
UTOPIA
C
ONFIGURATION
R
EGISTER
AND
THE
R
ESULTING
UTOPIA I
NTERFACE
H
ANDSHAKE
M
ODE
.
V
ALUE
UTOPIA I
NTERFACE
H
ANDSHAKE
M
ODE
0
The UTOPIA Interfaces operate in the octet level handshake mode.
1
The UTOPIA Interfaces operate in the cell level handshake mode.
F
IGURE
34. T
IMING
D
IAGRAM
OF
VARIOUS
T
RANSMIT
UTOPIA I
NTERFACE
BLOCK
SIGNALS
,
WHEN
THE
T
RANSMIT
UTOPIA I
NTERFACE
BLOCK
IS
OPERATING
IN
THE
“C
ELL
L
EVEL
H
ANDSHAKING
” M
ODE
.
TxClk
TxClav
TxEnB*
TxData[15:0]
TxSoC
W26
W0
W1
W2
W23
W24
W25
W26
W22
X
X
1
2
3
4
24
25
26
27
28
29
30