
PM73487 QRT
PMC-Sierra, Inc.
PMC-980618
Issue 3
622 Mbps ATMTraffic Management Device
Released
Datasheet
93
6.5
A microprocessor cycle starts when the chip select (/CS) and command (/ADS) are asserted. Dur-
ing read cycles, the device asserts /READY to indicate that data on the data bus is valid and dur-
ing write cycles the chip asserts /READY to indicate that the write has finished and data from the
bus can be removed. The microprocessor can terminate the current cycle at any time. As shown in
Figure 63, the device stops driving the bus and deasserts all control lines when the cycle termi-
nates. The current cycle terminates when the device select is deasserted or both read and write are
deasserted. A new cycle can start once the /READY has been deasserted. If the cycle was termi-
nated prematurely before the /READY was asserted, then a new microprocessor cycle can start
after one clock cycle.
Processor Interface Timing
Figure 63. Microprocessor Read Timing
Symbol
Parameter
Signals
Min
Max
Unit
Tcyc
Processor clock frequency
PCLK
12.5
50
MHz
Taddrsu
Input address setup time
ADDRDATA(31:0)
3
ns
Taddrh
Input address hold time
ADDRDATA(31:0)
1
ns
Tradsu
Address strobe setup time
/ADS
3
ns
Tradsh
Address strobe hold time
/ADS
1
ns
Tcssu
Chip select setup time
/CS
3
ns
Tcsh
Chip select hold time
/CS
1
ns
......
......
......
......
......
......
......
......
Tcyc
Tcssu
Tcsh
Tradsu
Tradsh
Taddrsu
Taddrh
Tdath
Twesu
Tweh
Trclkq
Trclkq
ADDR
MICROPROCESSOR READ CYCLE
DATA
PCLK
/CS
/ADS
ADDRDATA(31:0)
W_/RD
/INTR
/READY