external ram for at89s51

[eliezer faizal]

hello, i'm a newbie in microcontroller programming...
i have a project using at89s51, and i want to store a data in an external ram,
but i don't know what external ram i could use (the type, serie, and datasheet),
please could someone help me?

 

[kinjalgp]

You can use any SRAM upto 64KB like 6264, 62256 etc.
Datasheets can be found at www.alldatasheet.com

Interfacing schematic can be found at https://www.pjrc.com/tech/8051/board4/schematic.html

 

[eliezer faizal]

thanks!

hi kinjalgp,
thanks for a very quick reply! and it's really userful for me!
btw, i have another question, it's related to my project,
i want to use 3 heat sensors, lm35d, but i just want to use one adc0804, is it possible? if it's, what
can i use to bridge the 3 heat sensors with one adc0804? do i have to use 3 transistors, or scrs?
or do you have other opinion?
thank you,

 

[kinjalgp]

Since ADC0804 has 8-channels, you can connect 3 LM35 sensors to 3 channels of ADC.

I didnt really get your query about transistors/scr! Please rephrase your question.

 

[eliezer faizal]

hi kinjalgp,
i thought that i have to use 3 transistors in order to use three sensors with one adc0804 (for line
selection). i never thought that the 8 channels adc0804 provides could handle three sensors,
thanks for your input,
i never really use a 89s51 before. i used a dt-51 board, it's a packed modul contains 89c51,
lcd, two external rams, and a max. but to use that modul in my project could mean cheating.
so you may think that i'm a total newbie here
and, another question, i want to add two green+red leds for indicator. the one is for showing the status between data logging (the microcontroller saves data from heat sensor to the
sram), and idle (the microcontroller does nothing), and the other led is for showing the status whether the board is uploading the data into the computer (the computer gets saved data from
sram), and idle.
since the at89s51 has p0, p1, p2, and p3...can you suggest me which pin i could connect
the adc0804 to, and for two leds and sram?
btw, do i need to use a multiplexer between adc0804 and the sram?
thank you, and sorry for long question

 

[kinjalgp]

Since you need to interface external RAM, ports P0 and P2 will be used for that. So you can either use P1 or P3 pins for LED. You can interface ADC either on the external bus or directly connect to free port pins.

 

[eliezer faizal]

hi kinjalgp
i have another question, but it is about multiplexing.
can i use 74ls153 to multiplex the three sensors to the adc0804 (adc0804 only has one channel)? because i use electronic
workbench simulator, and when i connect the 74ls153 input pin with +3 vdc, its output pin
is +5 vdc. is it program malfunction?
if i may not use 74ls153, which multiplexer/driver do you suggest me?
thank you

 

[Nigel Goodwin]

hi kinjalgp
i have another question, but it is about multiplexing.
can i use 74ls153 to multiplex the three sensors to the adc0804 (adc0804 only has one channel)? because i use electronic
workbench simulator, and when i connect the 74ls153 input pin with +3 vdc, its output pin
is +5 vdc. is it program malfunction?
if i may not use 74ls153, which multiplexer/driver do you suggest me?
thank you

That's a logic switch, you need an analogue switch, there are a number of CMOS versions - 4066 etc.

 

[eliezer faizal]

hi nigel, thanks for the reply,
i only know few of electronic components, so thank you very much for mentioning the switch type (4066), i think i couldn't figure it out
by myself well, i have so many data from you guys, i think i'll try to build the project know, but...i think i'll be back soon to ask more questions
thanks again

 

[manjari]

hi i want to know how should i use ADC0804 and microcontroller8051 in order to convert my analog output from load cell in digital and interface it with computer using RS232. please help me doin that. thank you.