Omron CQM1H-SCB41 operation manual Transmission Methods

Using Protocol Macros Section 5-7

Transmission Methods

Although the following two transmission methods are commonly used, only half- duplex transmissions are supported for CQM1H protocol macros.

Half-duplex: Data can be sent only one direction at a time.

A B Or A B

Full-duplex: Data can be sent in both directions at the same time.

A B

The use of half-duplex transmissions presents some restrictions. Data received from just before the SEND operation through the end of the SEND operation cannot be received as receive data for the next RECEIVE operation because the reception buffer is cleared just before a sequence is executed and at the end of the SEND operation (i.e., for the SEND and SEND&RECEIVE commands).

Transmission	Reception buffer cleared	Data reception	Character trace
mode
Half-duplex	Just before sequence execution	Between end of SEND operation and end	All characters while
	and at the end of SEND operation	of RECEIVE operation or between the	tracing is being
	for SEND or SEND&RECEIVE	end of SEND operation and just before	performed
	commands	beginning of next SEND operation

An example timing chart for the above situation is shown below.

Sequence execution Reception buffer cleared

Data received

Character trace

Receive Send Receive

See note 1.

Note 1. Data received before the completion of the SEND operation will be lost, but it will be included in the character trace.

2.There is a time lag between the completion of data send processing and the end of the SEND operation. This time lag is time t1 and is shown in the fol- lowing table. If the response from the external device is too quick, any re- ceive data entering between the end of sending data for the SEND operation and the completion of the SEND operation will not be received.

SEND operation
Data send processing
	t1
Quick response	Time lag (see table)

Data not received here

Data reception

Reception buffer cleared

91