
CHAPTER 5 BUS CONTROL FUNCTION
User’s Manual U15905EJ2V1UD
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5.8.2
Bus hold procedure
The bus hold status transition procedure is shown below.
<1> HLDRQ = 0 acknowledged
<2> All bus cycle start requests inhibited
<3> End of current bus cycle
<4> Shift to bus idle status
<5> HLDAK = 0
<6> HLDRQ = 1 acknowledged
<7> HLDAK = 1
<8> Bus cycle start request inhibition released
<9> Bus cycle starts
Normal status
Bus hold status
Normal status
HLDAK (output)
HLDRQ (input)
<1> <2>
<5>
<3><4>
<7><8><9>
<6>
5.8.3
Operation in power save mode
Because the internal system clock is stopped in the software STOP and IDLE modes, the bus hold status is not
entered even if the HLDRQ pin is asserted.
In the HALT mode, the HLDAK pin is asserted as soon as the HLDRQ pin has been asserted, and the bus hold
status is entered. When the HLDRQ pin is later deasserted, the HLDAK pin is also deasserted, and the bus hold
status is cleared.