
XRT7245
DS3 UNI FOR ATM
á
PRELIMINARY
REV. 1.03
276
The user can configure the UNI to operate in one of
these two handshake modes by writing the appropri-
ate data to Bit 5 (Handshake Mode) of the UTOPIA
Configuration Register, as depicted below.
The following table specifies the relationship between
this bit and the corresponding Handshaking Mode.
Note:
1. The Handshake Mode selection applies to both the
Transmit UTOPIA and Receive UTOPIA Interface
blocks.
2. Since Multi-PHY mode operation requires the use
of “Cell-Level” Handshaking; this bit 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 in
order to configure “Octet- Level Handshaking, mode.
Figure 87 presents a timing diagram that illustrates
the behavior of various Receive UTOPIA Interface
block signals when the Receive UTOPIA Interface
block is operating in the “Cell Level” Handshake Mode.
Note:
regarding Figure 88
1. The Receive UTOPIA Data bus is configured to be
16 bits wide. Hence, the data, which the Receive
UTOPIA places on the Receive UTOPIA Data bus,
is expressed in terms of 16 bit words: W0–W26.
2. The Receive UTOPIA Interface block is configured
to handle 54 bytes/cell. Hence, Figure 88 illustrates
the ATM Layer processor reading in 27 words (W0
through W26) for each ATM cell.
In Figure 88, the ATM Layer processor is just finishing
up its reading of an ATM cell. Prior to clock edge #2,
the RxFIFO does not contain enough ATM cell data
to make up at least one cell. Hence, the Receive
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
R/W
R/W
R/W
R/W
R/W
R/W
T
ABLE
62: T
HE
R
ELATIONSHIP
BETWEEN
THE
CONTENTS
OF
B
IT
5 (H
ANDSHAKE
M
ODE
)
WITHIN
THE
UTOPIA
C
ONFIGURATION
R
EGISTER
,
AND
THE
RESULTING
UTOPIA I
NTERFACE
H
ANDSHAKE
M
ODE
V
ALUE
R
ESULTING
H
ANDSHAKE
M
ODE
0
The UTOPIA Interfaces operate in the cell level handshake mode.
1
The UTOPIA Interfaces operate in the octet level handshake mode.
F
IGURE
87. T
IMING
D
IAGRAM
OF
VARIOUS
R
ECEIVE
UTOPIA I
NTERFACE
BLOCK
SIGNALS
,
WHEN
THE
R
ECEIVE
UTOPIA I
NTERFACE
BLOCK
IS
OPERATING
IN
THE
“C
ELL
L
EVEL
” H
ANDSHAKE
M
ODE
RxClk
RxClav
RxEnB*
RxData[15:0]
RxSoC
W24
W25
W26
W0
W1
W2
W25
W26
1
2
3
4
5
6
7
8
9
31
32
34