1MAC306892-MB C Section 3
Vendor-specific implementation
RER620 23
Communication Protocol Manual
3.6.20 Cyclical period
• Min: 1
• Max: 604800
• Default: 10
• Unit: seconds
Cyclical period is the periodical timer for the cyclical data sending. The maximum of 
604800 seconds means one week.
3.6.21 Transmit window 
• Min: 1
• Max: 32767
• Default: 12
•Unit: APDU 
The value of k shall indicate the maximum number of sequentially numbered I format 
APDUs that the DTE may have outstanding (i.e. unacknowledged) at a given time. The 
transmitter stops the transmission at k unacknowledged I format APDUs. 
3.6.22 Receive window
• Min: 1
• Max: 32767
• Default: 8
•Unit: APDU
The receiver acknowledges at the latest after receiving w I format APDUs
Recommendation: w should not exceed two-thirds of k.
3.6.23 Transmit timeout
• Min: 1000
• Max: 255000
• Default: 15000
•Unit: ms
t1 is the timeout of a sent U-frame or I-frame. t1 starts after a U-frame or I-frame message 
is sent. When t1 timer expires and no ACK for that message was received, the connection 
termination (active close) will be initiated. The accuracy for t1 is 1 second. The timeout 
setting should be set as a multiple of 1000ms.
3.6.24 Receive timeout
• Min: 1000