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Manufacturer Specific Profile Area
Manual • Doc.-No.: C.3055.21 / Rev. 1.1
CAN-CBX-COM2
Page 108 of 125
8.12.2.8 Handshake_On, Handshake_Off
An overview of the communication parameters 2800
h
and 2900
h
is shown on page 95.
Parameter name
Handshake_Off
Handshake_On
Object index,
Sub-index
2800
h
, 07
h
(COM A)/
2900
h
, 07
h
(COM B)
2800
h
, 08
h
(COM A)/
2900
h
, 08
h
(COM B)
Access mode
rw
rw
Data type
unsigned 8
unsigned 8
Value range
00...FF
h
10...FF
h
Unit
n.a.
n.a.
Default value
F6
h
0A
h
Description:
By means of these parameters the handshake function of the serial interface can be
set for the data direction serial -> CAN (this function is not supported in RTS-
Modem Mode! See page 102).
The buffer for the serial data received has a capacity of 256 bytes. In order to prevent
the buffer from overflowing and data to be lost, the transmitter of the serial data can
be told via the handshake line RTS or via protocol byte <Xoff> to suspend
transmission until the buffer has capacity for new data again.
In parameter Handshake_On the number of bytes received in the Rx-buffer is
entered from which the serial data flow is to be suspended. In default setting this
value is F6
h
, i.e. if 250 bytes are in the Rx-buffer, the RTS-signal of the serial
interface will be activated. If XON/XOFF_EN is enabled by parameter
Tx_Start/Protocol, the software handshake <Xoff> also signalizes that the buffer is
not ready to receive.
In parameter Handshake_Off the number of bytes in the Rx-buffer is specified from
which the reception of serial data will be enabled again. In default setting this value
is 0A
h
, i.e. if only 10 bytes are left in the Rx-buffer, the RTS-signal of the serial
interface will be deactivated. If XON/XOFF_EN is enabled via parameter
Tx_Start/Protocol, the software handshake <Xon> also signalizes that the buffer is
ready to receive again.
The value of parameter Handshake_Off must always be smaller than the value of
parameter Handshake_On!
If the bit RTS_Mode = ‘0’, the RTS-signal always has the current handshake,
regardless of the bit XON/XOFF_EN.