Z85233 Datasheet, PDF (176/317 Pages) Zilog, Inc. – The Zilog SCC Serial Communication Controller

Application Note
The Z180™ Interfaced with the SCC at MHZ
Table 10. 10 MHz SCC Timing Parameters for Interrupt Acknowledge Cycle
No Symbol
13 TsIAi(RD)
14 ThIA(RD)
15 ThIA(PC)
38 TwRDA
39 TwRDA
40 TdRDA(DR)
41 TsIEI(RDA)
42 ThIEI(RDA)
43 TdIEI(IEO)
Parameter
/INTACK Low to /RD Low Setup
/INTACK High to /RD High Hold
/INTACK to PCLK High Hold
/INTACK Low to /RD Low Delay
(Acknowledge)
/RD (Acknowledge) Width
/RD Low (Acknowledge) to
Read Data Valid Delay
IEI to /RD Low (Acknowledge)
Setup Time
IEI to /RD High (Acknowledge)
Hold Time
IEI to IEO Delay
Min
Max
Units
130
ns
7
0
ns
30
ns
125
ns
125
ns
120
ns
95
ns
0
ns
175
ns
Table 11. Z180 Timing Parameters Interrupt Acknowledge Cycles (Worst Case Z180)
No Symbol
10 tM1D1
14 tM1D2
15 tDRS
Parameter
Clock High to /M1 Low
Clock High to /M1 High
Data to Clock Setup
16 tDRH
Data Read Hold Time
28 tIOD1
Clock LOW to /IORQ Low
29 tIOD2
30 tIOD3
Clock LOW to /IORQ High
/M1 Low to /IORQ Low Delay
Note: Parameter numbers in this table are the numbers in the Z180 technical manual.
Min
Max
60
60
25
0
50
50
200
Units
ns
ns
ns
ns
ns
ns
ns
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.
UM010901-0601
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