TBlockSerial.RecvByte
TBlockSerial

function RecvByte(Timeout: Integer): Byte;

Unit
SynaSer

Description
Waits until one data byte is received which is also returned as function result. If no data is received within TIMEOUT (in milliseconds) period, LastError is set to 30.

Timeout is defined as maximum time between two bytes of data, not as timeout for all operation!