Toshiba TX39 user manual Bus Arbitration, Bus request and bus grant

TMPR3901F

4.5Bus Arbitration

4.5.1Bus request and bus grant

An external bus master can request that the TMPR3901F grant control of the bus. This is done by asserting the BUSREQ* signal. In response, the TMPR3901F will release the bus and assert a BUSGNT* signal.

If BUSREQ* is asserted, while the TMPR3901F is already engaged in a bus operation cycle, the TMPR3901F will not relinquish the bus until that cycle is completed.

Figure 4-8 shows timing for a bus request and bus grant during which the TMPR3901F relinquishes the bus and an external bus master acquires the bus.

		MPU
MPU cycle	DMA cycle	cycle
SYSCLK
A[31:2]
BE[3:0]*
RD*
WR*
BSTART*
LAST*
BURST*
BSTSZ[1:0]
BUSREQ*
BUSGNT*
SNOOP

Figure 4-8 Bus arbitration

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