CALL JJINPUT - MSX Wiki

Effect

Enables or disables a text transmission synchronization mode between the connected MSX and PC (Windows) computers.

Notes:

If communication is interrupted while the synchronization mode is ON, the MSX side will freeze while waiting for communication. Be sure to perform _JJINPUT (0) to end the synchronization mode before disconnecting the communication.
Since the program for synchronous mode resides at the end of the "File control block (FCB)" in the BASIC work area, an error will occur if the maximum number of files in MSX-BASIC is 0 (MAXFILES = 0).
Do not issue file operation instructions such as OPEN or PRINT # 1 while the synchronization mode is ON (SAVE, LOAD, etc. are okay). If you really want to use such instructions, set MAXFILES = 2 or higher before turning on the synchronization mode.

CALL JJINPUT (<SyncMode>)

<SyncMode> is a number to enable or disable the synchronization mode:

0 = synchronization mode OFF - required to execute other serial communication instructions - it's also recommended to press the [SYNC OFF] button on the Windows side.
1 = synchronization mode ON - Windows and MSX communicate every 1/60 second and immediately transfer the text entered in the text transmission window of "Joy Joy File Server" (Windows) to the MSX side. The color of the input window turns pink. If you enter text in this state and press ENTER, the text in the input window will be transferred to the MSX side.

CALL JJINPUT (1)