coltoff@PRC.Unisys.COM (Joel Coltoff) (12/08/88)
Does anyone know of a real time clock chip that can interface directly
to an 8051. Everyone I've seen so far is to slow to interface at 16 MHz.
The 8051 can't be wait stated so there aren't many options. I really don't
want to latch the data and extend the WR & RD pulses with one shots.
Any advice would be greatly appreciated. Samples would be nice too.
--
- Joel
{psuvax1,sdcrdcf}!burdvax!coltoff (UUCP)
coltoff@burdvax.prc.unisys.com (ARPA)gbell@pnet12.cts.com (Greg Bell) (12/08/88)
This may be a silly question, but have you tried National Semi's
MM58167, MM58174, or MM58274 ?
The only docs I have are on the '167 and its just a "design guide" (ie. no
timing specs).
Greg Bell_________________________________________________________
Hardware hacker |
Electronics hobbyiest | UUCP: { uunet ncr-sd }!pnet12!gbell
EE major at UC San Diego |gmg@hcx.uucp (Greg M. Garner) (12/09/88)
In article <8519@burdvax.PRC.Unisys.COM>, coltoff@PRC.Unisys.COM (Joel Coltoff) writes: > Does anyone know of a real time clock chip that can interface directly > to an 8051. Everyone I've seen so far is to slow to interface at 16 MHz. > The 8051 can't be wait stated so there aren't many options. I really don't > want to latch the data and extend the WR & RD pulses with one shots. > Any advice would be greatly appreciated. Samples would be nice too. > -- > - Joel > {psuvax1,sdcrdcf}!burdvax!coltoff (UUCP) > coltoff@burdvax.prc.unisys.com (ARPA) How about using the mostek 48T02 real time battery backed static ram? This little beauty has a real time clock in it, with a crystal, and it even has a lithium battery mounted in it! It also has software calibration, software battery fail detection, and almost 2K of battery backed ram. You can get these in 200ns, 150ns, not sure about 100ns. I don't know a lot about the 8051, so I don't know if this is fast enough, but I suspect that it is. These can be gotten from Schweber, or mostek. Good luck! Greg Garner 501-442-4847 USENET: ...!uunet!harris.cis.ksu.edu!hcx!gmg
cook@stout.ucar.edu (Forrest Cook) (12/10/88)
In article <1395@cseg.uucp> gmg@hcx.uucp (Greg M. Garner) writes: >In article <8519@burdvax.PRC.Unisys.COM>, coltoff@PRC.Unisys.COM (Joel Coltoff) writes: >> Does anyone know of a real time clock chip that can interface directly >> to an 8051. Everyone I've seen so far is to slow to interface at 16 MHz. >How about using the mostek 48T02 real time battery backed static ram? I have used one of these clock chip/rams for over a year now and am quite happy with its performance (with a Z-80). There is no crystal trimmer cap, so the trimming is done with a special pulse adder/stealer circuit that can be set to add or subtract pulses every N minutes where N is stored in a special register. I have heard that HP uses a similar technique in their HP41 calculator. The expected lifetime of the lithium cell is about 10 years if I remember correctly, longer if the chip is usually powered up. Maybe Mostek could come out with a 32K X 8 Ram with the same clock... ^ Forrest Cook (The preceding comments were my Opinions) ^ /|\ /|\ /|\ {husc6 | rutgers | ames | gatech}!ncar!stout!cook /|\ /|\ {uunet | ucbvax | allegra | cbosgd}!nbires!ncar!stout!cook /|\