Zilog Z16C35 Manual do Utilizador descarregar pdf (Página 194)

Application Note

The Z180™ Interfaced with the SCC at MHZ

7-17

During an Interrupt Acknowledge cycle, the SCC requires

both /INTACK and /RD to be active at certain times. Since

the Z180 does not issue either /INTACK or /RD, external

logic generates these signals.

The Z180 is in a Wait condition until the vector is valid. If

there are other peripherals added to the interrupt priority

daisy chain, more Wait states may be necessary to give it

time to settle. Allow enough time between /INTACK active

and /RD active for the entire daisy chain to settle.

There is no need of decoding the RETI instruction used by

the Z80 peripherals since the SCC daisy chain does not

use IP, except during Interrupt Acknowledge. The SCC

and other Z8500 peripherals have commands that reset

the individual IUS flag.

External Interface for Interrupt Acknowledge Cycle: The

bottom half of Figure 14 is the interface logic for the

Interrupt Acknowledge cycle.

Table 10. 10 MHz SCC Timing Parameters for Interrupt Acknowledge Cycle

No Symbol Parameter Min Max Units

13 TsIAi(RD) /INTACK Low to /RD Low Setup 130 ns

14 ThIA(RD) /INTACK High to /RD High Hold 0 ns

15 ThIA(PC) /INTACK to PCLK High Hold 30 ns

38 TwRDA /INTACK Low to /RD Low Delay 125 ns

(Acknowledge)

39 TwRDA /RD (Acknowledge) Width 125 ns

40 TdRDA(DR) /RD Low (Acknowledge) to

Read Data Valid Delay

120 ns

41 TsIEI(RDA) IEI to /RD Low (Acknowledge) 95 ns

Setup Time

42 ThIEI(RDA) IEI to /RD High (Acknowledge) 0 ns

Hold Time

43 TdIEI(IEO) IEI to IEO Delay 175 ns

Table 11. Z180 Timing Parameters Interrupt Acknowledge Cycles (Worst Case Z180)

No Symbol Parameter Min Max Units

10 tM1D1 Clock High to /M1 Low 60 ns

14 tM1D2 Clock High to /M1 High 60 ns

15 tDRS Data to Clock Setup 25 ns

16 tDRH Data Read Hold Time 0 ns

28 tIOD1 Clock LOW to /IORQ Low 50 ns

29 tIOD2 Clock LOW to /IORQ High 50 ns

30 tIOD3 /M1 Low to /IORQ Low Delay 200 ns

Note: Parameter numbers in this table are the numbers in the Z180 technical manual.

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