ACU-RITE MILLPWR G2, Technical Manual

Page: 531 / 546

7.6 Configuring the Serial Interface 531
Hardware
handshaking Data transfer is controlled by electrical signals. Information, such as Clear to
Send (CTS), Request to Send (RTS), “Start transmission” and “Stop transmis-
sion” is passed on by the hardware.
Example:
When a computer is to transmit a character, it checks the CTS signal line to
see whether it is active (ON). If it is, the character is transmitted.
Hardware handshaking requires

the data lines TXD and RXD (transmitted and received data)

the RTS control line (switching on transmitting unit)

the CTS signal line (Clear to Send)

a ground connection
The DTR and DSR signals indicate the operational status of the LE and periph-
eral device:

DTR: Interrogated by peripheral; it is logic one if LE is ready for operation.

DSR: Interrogated by LE.
• LOW level means: external data input/output not ready.
• HIGH level means: external data input/output ready.

Data output from the control to EXT
When the receiving buffer is full, the external device resets the RTS signal.
The control detects that the peripheral unit receiving buffer is full at its CTS
input:
Activating
+ positive voltage level
- negative voltage level