External Bus Interface
MOTOROLA
MPC823e REFERENCE MANUAL
13-9
EXTERNAL BUS
13
INTERFACE
13.4.2.1 SINGLE BEAT READ FLOW.
The basic read cycle begins with a bus arbitration,
followed by the address transfer and the data transfer. The handshakes are illustrated in the
following diagrams as applicable to the fixed transaction protocol.
Figure 13-3. Basic Flow Diagram of a Single Beat Read Cycle
REQUEST BUS (BR)
RECEIVES BUS GRANT (BG
) FROM ARBITER
ASSERTS BUS BUSY (BB
) IF NO OTHER MASTER IS DRIVING
ASSERT TRANSFER START (TS
)
DRIVES ADDRESS AND ATTRIBUTES
RECEIVES ADDRESS
RETURNS DATA
ASSERTS TRANSFER ACKNOWLEDGE (TA
)
RECEIVES DATA
SLAVE
MASTER
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