| ??? 07/26/07 15:10 Read: times |
#142354 - confusing input Responding to: ???'s previous message |
Scott P. Dolan said:
I am reverse engineering a S-Plus slot machine so, I can control the functionality of the machine. The board has DUART with two custom transciever and recievers. I believe transmitter convert the TTL voltage to RS-232 as the transmitter output 0-8Volts. The problem is the quiescent state of the TTL is High. I believe this state needs to be Low. Does any know if it is possible to invert the Tx and Rx signal on SCN2681 (DUART)
Currently the TTL tx signals HHHHH-DDDDD-HHHHHHH H = 5V L = 0; D = 5->0V / 0->5V Currently the Tx output signals are HHHHH-DDDDD-HHHHHHH H = 8V L = 0; D = 8->0V / 0->8V The desire TTL tx signal are LLLLLLL-DDDDDD-LLLLLLL H = 5V L = 0; D = 5->0V / 0->5V IF this is supposed to be RS232 signaling, the levels are all wrong. Legal RS232 levels, IIRC, are either >3.0 volts or < than -3.0 volts. Nothing between those two levels with respect to GND (common) is defined. What does "HHHHH-DDDDD-HHHHHHH" mean? At what rate are you sampling the data? The "standard" rate for the SCN2681 timebase is 3.6864 MHz. Is that the rate it's using? Normal RS232 follows the protocol Russel indicated, i.e. the idle state is the high voltage on the RS232 data lines. The output from the SCN2681 should, therefore, be at ~0 volts during idle periods. When you say "custom" to describe the transceiver, what, exactly, do you mean? Does it say "custom" on it? Does it have any numbers or logo at all? There are parallel I/O signals on a DUART. What are they doing? RE |
| Topic | Author | Date |
| (DUART) SCN2681 Dual asynchronous rx/tx | 01/01/70 00:00 | |
| Default IDLE is high | 01/01/70 00:00 | |
| confusing input | 01/01/70 00:00 | |
| Confusion? | 01/01/70 00:00 | |
Yes, I lied ... | 01/01/70 00:00 |