Appendix c - rs485 wiring diagrams – Lathem DDC2 User Manual
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DDC2 / 4-RS -485 Wiring
Digital Display Wall Clock Guide
Page 46
Appendix C - RS485 Wiring Diagrams
RS485 Data Format
The data string that sends the time to the DDC2 / DDC4 Series Wall Clocks is formatted in such a manner
that a utility can be written to achieve time updates from a personal computer. The following table shows
the layout and explains each character.
Data Format
0#112233445566777Z,CR
The data string is compiled of a total of 16 characters. These characters represent the following.
0
Address byte
#
Command for Time update
11
Hex for Seconds (01-59)
22
Hex for Minutes (00-59)
33
Hex for Hour (00-23)
44
Hex for Day of Week (Sunday = 0)
55
Hex for Month (01-12)
66
Hex for Date (01-31)
777
Hex for Year offset from 1984 (000-127)
Z
The Checksum (1's compliment of the mod-64 sum of all characters in the string except the CR and
the Checksum)
CR
Carriage Return
Transfer of the above string must be done at 9600 Baud, 8 Data Bits, 1 Stop Bit and No Parity.
Requires the SWIFT-485 plus to convert the RS232 signal from the PC to RS485 to send data to the DDC
Series Wall Clocks.
Note: Lathem does not offer a utility to perform this function. This information is supplied so that a 3
rd
party may create such a utility.