HD64570 Datasheet, PDF (51/469 Pages) Hitachi Semiconductor – Serial Communications Adaptor

1.7.12 Bus Arbiter
The SCA has a built-in bus arbiter for arbitrating the bus between the on-chip DMAC and an
external bus master device. This bus arbiter provides an easy way to design a multi-channel
system using two or more SCA chip (figure 1.23). The circuit shown here merely represents the
concept of the multi-channel system. In practice, the user system should be designed while
referring to the bus arbitration sequence (figure 3.6).
MPU
HD64180,
etc.
BUSACK BUSREQ
Glue logic
+5V
BUSREQ BUSY
BUSACK BEO
BUSREQ BUSY
BUSACK BEO
BUSREQ BUSY
BUSACK BEO
BUSREQ BUSY
BUSACK BEO
SCA
SCA
SCA
SCA
Figure 1.23 Daisy-Chained Multi-Channel System (example)
Rev. 0, 07/98, page 35 of 453