89ls52 could be use on 3 voltsbobsanjose said:That is a little strange. As you mentioned the 89C52 has only one UART, so the hardware has to be modified. Whether that is by adding a multiplexing scheme or by an external 2x UART that you can address either through the external bus or by bitbanging. Either way, a gps receiver and a gsm modem running at the same time could be A LITTLE too much to handle for a regular 8051 type device. At 24 MHz you execute approx. 1.5 MIPS all 8-bit data. So if incoming data are wider than 8-bit the speed will come to a crawl.
There are a few options:
Depending on the package you are using there could be a replacement device that is very close in signals and has 2 UARTs. It is called LPC952 from NXP. There are some differences though from a hardware standpoint.
1. Reset is active low
2. The LPC is a 3V device, the 89C52 a 5V device
3. It is a 2-clock core, 6x faster than the original 8051. At 16 MHz it is actually 4x faster than the 89C52 running at 24 MHz.
4. Flash programming algorithms are different
As you need to change the hardware, you might as well use a better micro!?
As for software, changes will be minimal, both are 51-based and can use the same tools to generate a program.
Other options with enough horsepower and 2 serial interface could be
STM32 low-end
LPC2103
Both ARM based 32-bit micros similar pricing to 89C52 but much more powerful and with 2 serial interfaces.
Hth, Bob
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Most systems can not guarantee that one event comes after the other. So, what if both, the GPS and the GSM start sending at the same time. No matter how slow it is, there is a problem that needs a higher layer protocol to resolve.shingadaddy said:Multiplexing can be done if you're not needing to be doing things at the same time or very terribly fast.
So has pretty much every other vendor. The LPC95x is probably as close to the device in use as a BMW 5 to a BMW 5M while the Renesas device would be more like a Cadillac and a BMW. Meaning, he should first try to find something very similar.shingadaddy said:Renesas has several controllers with multiple uarts.
If you are referring to a relay just as a switch, sure you can use a switch but that switch should rather be a logic gate as there is no need to drive any significant amount of current.siva_2smart said:I dont communicate with the two devices at a time ... So cant i use a relay ...
my question is CAN I USE A RELAY
iftikhar_abid said:dear u can use a simpl trick just use 2 addresses to enable one at a time......but in this way u will b able to access one at a time.
for further help u can mail me.
iftikhar_abid(at)yahoo.com
Regards,
Iftikhar Abid
siva_2smart said:Hi !!!
I need to inteface a gps receiver and gsm modem to a single at89c52 microcontoller.But my microcontroller has single rxd and txd pins. Can anyone tell me how to do this...
HELP NEEDED URGENTLY... thanks in advance
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