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CHAPTER 3 FUNCTIONAL DESCRIPTION
User’s Manual S14054EJ4V0UM
37
Table 3-2. FDQ Pins and Transmit Data Attributes (64-Bit Single Bus)
FDQ pins
Data Attribute
Valid Data Byte Position
[3]
[2]
[1]
[0]
Little Endian
Big Endian
0
0
0
0
Idle
–
–
0
0
0
1
Data start
FD[63:0]
FD[63:0]
0
0
1
0
Intermediate data
FD[63:0]
FD[63:0]
0
0
1
1
Data start (with CRC appended)
FD[63:0]
FD[63:0]
0
1
×
×
Reserved
–
–
1
0
0
0
Data end 0
FD[63:0]
FD[63:0]
1
0
0
1
Data end 1
FD[7:0]
FD[63:56]
1
0
1
0
Data end 2
FD[15:0]
FD[63:48]
1
0
1
1
Data end 3
FD[23:0]
FD[63:40]
1
1
0
0
Data end 4
FD[31:0]
FD[63:32]
1
1
0
1
Data end 5
FD[39:0]
FD[63:24]
1
1
1
0
Data end 6
FD[47:0]
FD[63:16]
1
1
1
1
Data end 7
FD[55:0]
FD[63:8]
For details of little endian and big endian, refer to
3.7.1 (4) Little endian/big endian
.
Once data start has been written, the rest of the data is written to the transmit FIFO by means of burst transfer.
If the quantity of the data in the transmit FIFO exceeds the value set to the TFDWH field of the TFIC register, the
TXFBAn signal goes low. By specifying idle in the middle of burst transfer, writing to the transmit FIFO can be
postponed.
By changing TXFPT[2:0] while data is written to the transmit FIFO, the transmit data can be written to the
transmit FIFO of another port. In this case, the data can be written to other port at the rising edge of FCLK
immediately after TXFPT[2:0] has been changed. However, it is necessary to confirm that the TXFBA signal
corresponding to the other port is high. The data stream written to the other port can be started from data having
any attributes of the data start, intermediate data, and end data, so that the transmit packet can be divided into
blocks and sequentially written to each of the ports. Each time a port is changed, however, the attribute of the
data to be written must be correctly provided to it. Figure 3-6 shows an example of changing the port to which
the transmit data is to be written using TXFPT[2:0].