Toshiba T2N Instruction Manual page 75

2. Data handling and data segmentation in TCP socket interface transmission and reception
a. When using the TCP socket interface for data transmission, the data transmitted in a single
operation is handled by the receive side Ethernet Port as one section of a continuous data
stream that comes from the sender. (See figure 6.6.)
In this technique, the data is not handled as a single unit, as it is in UDP socket interface
transmission.
b. The amount of data transmitted to the T2N from the TCP socket interface due to a T2N
receive request will vary depending on both the timing with which the T2N issues the receive
request, and the timing with which the data arrives at the TCP socket interface.
c. In the Ethernet Port TCP socket interface, up to 4380 bytes of received data can be stored per
socket. Also note that up to 2000 bytes of data can be transferred to the T2N for a single
receive request from the T2N. For example, if the remote port sends 800 bytes at a time, then
the amount of received data per socket may be either 800, 1600, 2400, 3200, or 4000 bytes. If
the amount of received data is 800 or 1600 bytes, those 800 or 1600 bytes can be acquired by
the T2N by a receive request from the T2N. In cases where the amount of received data is
2400, 3200, or 4000 bytes, 2000 bytes will be transferred by the first receive request from the
T2N, and the remaining 400, 1200, or 2000 bytes can be transferred by issuing another
receive request from the T2N.
d. Therefore, to handle one unit of transmitted data as a single unit of data on the receiving side
as well, at the system design stage users must analyze both the data format (head/tail
delimiting codes, data sequencing) and the amount of data to be transmitted, and provide
routines to decode the transmitted data in the receiving T2N user software.
e. Allocate an area one word larger than the transmitted data size as the T2N register
area that will hold the received data. As the result of a receive request, information
indicating the size of the transmitted data for the single operation plus the data transmitted in
the single operation will be stored in that area.
Transmitted data
Figure 6.6
Ethernet Port TCP socket interface
Consecutive data (up to 4380 bytes)
Data received up to this
time
Max: 2000 bytes
Receive response
Handling of Transmitted Data in the TCP Socket Interface
74
6 F 3 B 0 3 6 2
T2N
Receive request
Data received by
the T2N
Transferred data