RX-64
RS485 UART
RS485 UART is a serial communication method that TxD and RxD cannot be executed
simultaneously. It is usually used when connecting several communication equipments
to one BUS. Since multiple devices are connected to the same BUS, all other devices
should be in the input state while a device transmits. The communication direction of
Main Controller controlling RX-64 is set as input and is changes to output only in the
course of transferring Instruction Packet.
Return Delay Time
Instruction Packet
Status Packet
RS485 Direction Output Duration
Return Delay Time
It is the time that takes to returns Status Packet after RX-64 receives Instruction Packet.
Default value is 160uSec. Return Delay Time can be changed by changing the data of
Control Table Address 5. Main Controller should convert Direction Port into the input
state within the Return Delay Time frame after sending Instruction Packet.
Tx, Rx Direction
Rs485 UART should change Direction into the receiving mode at the time of finishing
transmission. In general, CPU has the following BITs showing UART_STATUS in the
register.
TXD_BUFFER_READY_BIT : It indicates the state that Transmission DATA can be
loaded into Buffer. However, it does not mean that previously transmitted data is
removed from CPU, but it means that SERIAL TX BUFFER is empty.
TXD_SHIFT_REGISTER_EMPTY_BIT : It is set when all Transmission Data is unloaded
from CPU. In case of TXD_BUFFER_READY_BIT, this bit is used when sending a byte
in serial communication as shown in the following example.
TxDByte(byte
bData)
{
while(!TXD_BUFFER_READY_BIT); //wait until data can be loaded.
SerialTxDBuffer = bData; //data load to TxD buffer
}
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