mcf5407 Freescale Semiconductor, Inc, mcf5407 Datasheet - Page 458

• Manufacturer Part Number: mcf5407
• Description: Mcf5407 Coldfire Integrated Microprocessor User
• Manufacturer: Freescale Semiconductor, Inc

General Operation of External Master Transfers
In Figure 18-30, the external device is bus master during C1 and C2, releasing control in
C3, at which time the external arbiter asserts BG to the MCF5407. During C4 and C5, the
MCF5407 is implicit master because no internal access is pending. In C5, an internal bus
request becomes pending, causing the MCF5407 to take explicit bus mastership in C6 by
asserting BR and BD. In C7, the external device removes the bus grant to the MCF5407.
The MCF5407 does not release the bus (the MCF5407 asserts BD) until the transfer ends.
18-30
SIZ[1:0], TM[2:0]
A[31:0], TT[1:0]
Figure 18-30. Three-Wire Implicit and Explicit Bus Mastership
D[31:0]
CLKIN
The MCF5407 can start a transfer in the CLKIN cycle after BG
is asserted. The external arbiter should not assert BG to the
MCF5407 until the previous external master stops driving the
bus. Asserting BG during another external master’s transfer
may damage the part.
R/W
TIP
BG
BR
BD
TS
AS
TA
C1
External Master
C2
MCF5407 User’s Manual
C3
NOTE:
C4
Mastership
Implicit
C5
C6
MCF5407
C7
Mastership
Explicit
C8
C9