| ??? 07/01/05 02:48 Read: times |
#96358 - Timing Calculations Responding to: ???'s previous message |
Salaam,
TRLRH(RD Pulse Width) >= tRR(peripheral's read pulse width) Some peripherals require a minimum time for the RD# signal to be active. An example is 8255A. TWLWH(WR Pulse Width) >= tWW or tWP(Write Pulse Width of the RAM) A minimum pulse width is required for the write signal by RAM. TRLDV(RD to Valid Data In) >= tOE(memory component's Output Enable to Output Valid or Output Enable Access Time) How much time the memory system has to return data after the controller drives the READ line active low. TRHDX(Data Hold After RD) <= tOH(memory component's Output Hold from Address Change) The minimum time the controller requires that data remain valid after the READ pin has gone inactive. TRHDZ(Data Float After RD) >= tDF or tDH(memory component's Data Hold from End of Write-Time) The memory device must be able to get the data off (float) the bus in time for the CPU to drive the next Address or bus contension may occur. TLLDV(ALE to Valid Data In) >= tACS or tACE(time from CS# low to data valid or Chip Enable Access Time) Corresponds to the access time of the data memory when ALE is used to drive the chip select pin of the memory device. TAVDV(Address to Valid Data In)????? TLLWL(ALE to WR or RD) >= tCW(time of chip select to end of write) The time between ALE going low to the read or write signal going low. This parameter is helpful if ALE is used as the chip select signal to the RAM. *70ns or even 55ns SRAM can't be used with 24MHz@x2 TAVWL(Address to WR or RD) >= tAS(address setup time in the RAM device) The time between a valid address and the read or write signal going low. TQVWX(Data Valid to WR Transition) Data setup time for the components which use the negative edge of the WR# signal to clock the data in. Most RAM devices, however, use the rising edge of the WR# signal to latch the data. TQVWH(Data Set-up to WR High) >= tDW(data valid to the end of WR# or Data to Write Time Overlap) How long the data is valid before the write signal goes high. TWHQX(Data Hold After WR) >= tDH(Data Hold from End of Write-Time or data hold time after the end of write) The minimum time that data is held after the WR# signal goes high. TRLAZ(RD Low to Address Float) The controller must float the bus before the memory device drives it with the data. Most RAM devices do not have a paramter that corresponds to TRLAZ. TWHLH(RD or WR High to ALE high) Is not used by memory devices, but other components which share the address data bus may be able to use this period. This time is considered to be dead time for the controller and the memory system. This is the original source from which I have extracted the timings and added some editions |
| Topic | Author | Date |
| MOVX TIMING WAVEFORMS | 01/01/70 00:00 | |
| bible | 01/01/70 00:00 | |
Here it is? | 01/01/70 00:00 | |
| Timing Calculations | 01/01/70 00:00 | |
| something more substantial | 01/01/70 00:00 |