HD64570 Datasheet, PDF (205/469 Pages) Hitachi Semiconductor – Serial Communications Adaptor

Station
T
Station
A (0)
Station
B (1)
Address Data Address Data
MP = 1 MP = 0 MP = 1 MP = 0
Station
C (2)
Station
D (3)
Figure 5.22 MP Bit Operation Example
In figure 5.22, T is a transmit station, and A, B, C, and D are receive stations. Receive stations A,
B, C, and D are assigned addresses 0, 1, 2, and 3, respectively.
For transmitting data from T to B, transmit station T sends address (1), with MP bit set to 1, to the
communication path. The receive stations all monitor the communications path. When they
receive data with the MP bit = 1, they assume the data is a station address and compare it with
their own address. In this example, the received data matches the address of station B. Station B
now assumes that it is the destination of subsequent data with the MP bit = 0. Other receive
stations A, C, and D, issue a search MP bit command and ignore the data with the MP bit = 0.
Thus, the transmit station can send data to a specific receive station by transmitting the destination
address, with the MP bit set to 1, and then transmitting the data, with the MP bit set to 0.
If the transmit station wants to send data to a different receive station, it transmits the new station
address, with the MP bit set to 1, to clear the search MP bit command. The transmit station can
use the same procedure as described above to communicate with any desired receive station.
Rev. 0, 07/98, page 189 of 453