| ??? 02/15/05 04:57 Modified: 02/15/05 05:01 Read: times |
#87472 - Loader circuitry for ultra high-speed... Responding to: ???'s previous message |
Christian Kleiber said:
I looked at the circuit for Dallas MCU in Fig 1 (Physical Connection, DS89C420/430/440/450-Based Designs) in this link
http://www.maxim-ic.com/appnotes....umber/3262 Now, from what i understood of the buffer is thatR1out from MAX232 is connected to both of the inputs of the buffer. The page says "When DTR is active (low state), it enables the buffers to turn on, driving the multiple signals that activate the bootloader". Am i correct? This is correct. There are three conditions required to activate the ROM loader in these devices: 1. RST must be high 2. /EA must be low 3. /PSEN must be low Not explicitly mentioned but very important is that upon exiting the loader, /EA needs to be high no later than the time that RST goes low. Otherwise you will be executing code from a non-existant external program store. My guess is that the author's intention was to guarantee this requirement is met by virtue of of the fact that the falling edge of RST (it pulls itself down in normal operation) will always lag the rising edge of /EA by tPLZ of the buffer. --Sasha Jevtic |
| Topic | Author | Date |
| Loader for DS89C420/30/40/50 | 01/01/70 00:00 | |
| Dallas loader | 01/01/70 00:00 | |
| Loader problems | 01/01/70 00:00 | |
| Dallas loader | 01/01/70 00:00 | |
| Dallas loader | 01/01/70 00:00 | |
| Don't discount 98 | 01/01/70 00:00 | |
| Don't discount 98 | 01/01/70 00:00 | |
| Linux version | 01/01/70 00:00 | |
| Linux version | 01/01/70 00:00 | |
| Terminal emulator in Linux? | 01/01/70 00:00 | |
serial loader exit timing | 01/01/70 00:00 | |
| Loader circuitry for ultra high-speed... | 01/01/70 00:00 | |
| Loader circuitry for ultra high-speed... | 01/01/70 00:00 | |
| Confusing figure 1 | 01/01/70 00:00 |