8051 Family
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The Intel 8051 is a single chip microcontroller which was developed by Intel in 1980 for use in embedded systems. It has become very popular in the 80s, but today many manufacturers propose enhanced versions that are 8051-compatible.
Architecture
Speed
| Name | Clock freq. | clock / instr. cycle(*) |
|---|---|---|
| Standard 8051 | 12MHz 16MHz 20MHz 24MHz |
12 |
| NXP P89V66x NXP P89CV51Rx2 |
0MHz..40MHz | 12 |
| 20MHz | 6 | |
| NXP P8xC660X2/661X2 NXP P87C51RX2 |
0MHz..33MHz | 12 |
| 0MHz..30MHz | 6 | |
| NXP LPC938 | 12MHz 18MHz |
2 |
(*) # clock oscillation periods / instruction cycle.
Expanded RAM
Intel 8XC51RA series uses a trick called Expanded RAM to allow accessing 512 byte of on-chip RAM memory. See 8XC51RA/RB/RC Hardware Description for detailed information.
In summary, there are 4 RAM memory segments:
| Lower 128 bytes of RAM | 00h..7Fh | DIRECT | INDIRECT | |
| Upper 128 bytes of RAM | 80h..FFh | INDIRECT | ||
| Special Function Registers (SFR) | 80h..FFh | DIRECT | ||
| 256-byte expanded RAM (ERAM) | 00h..FFh | MOVX @R0 MOVX @R1 MOVX @DPTR (EXTRAM=0) |
Links
- The 8051 on Wikipedia.
- My links on Del.icio.us.
- A website on 8051/8052 controllers [1].
Intel
- Documentation page.
- MCS 51 core
- MCS 51/251 - Classic
- 128 byte on-chip data RAM
- Main page
- 87C51/80C51BH/80C31BH Commercial/Express version
- 80C31BH/80C51BH/87C51 Automotive version
- MCS 51/251 - Expanded RAM
NXP
NXP (ex. Philips Semiconductors) offers a wide range of 8051-compatible controllers:
- LPC900 family