| ??? 03/31/05 19:33 Read: times |
#90768 - Sausage and Chips Responding to: ???'s previous message |
Donald Catto said:
"Anyone know why Intel decided to have 4 banks of 8 registers in the original 8051?"
No, but you could look at it the other way - why not? You have a choice of using certain memory locations as registers or as plain RAM - increased flexibility at no extra cost. Indeed, but why stop at 4 then? There is a spare bit in the PSW so why not have 8 banks - there are no additional instructions necessary to do this as there are no bank specific instructions. My best guess would be they were thinking most apps would have perhaps 3 interrupt routines (serial, timer and port pin) so bank switching is the fastest way to push all 8 regs. But I am still stumped to think why 8 registers. Actually, now I come to think about it I seem to remember reading some code by Intel that used the banks as part of their 8051 OS. I'll go ferret it out. Thanks for jogging the old grey cells Donald. Ian |
| Topic | Author | Date |
| Registers | 01/01/70 00:00 | |
| my guess | 01/01/70 00:00 | |
| Participation | 01/01/70 00:00 | |
| Old Age | 01/01/70 00:00 | |
| Old but stronger still | 01/01/70 00:00 | |
| just a guess | 01/01/70 00:00 | |
| Powers of Two | 01/01/70 00:00 | |
| when all was new | 01/01/70 00:00 | |
| push and pop | 01/01/70 00:00 | |
| passing | 01/01/70 00:00 | |
| Passing Parameters | 01/01/70 00:00 | |
| yes, with a monitor | 01/01/70 00:00 | |
| Register Overlaying??? | 01/01/70 00:00 | |
| Context | 01/01/70 00:00 | |
not necessarily | 01/01/70 00:00 | |
| my point was | 01/01/70 00:00 | |
| Sausages | 01/01/70 00:00 | |
| Sausage and Chips | 01/01/70 00:00 | |
| no instructions, but gates | 01/01/70 00:00 | |
| Many Gates? | 01/01/70 00:00 |