Lathem Understanding RS 485 Wiring Diagram for Digital Wall Clocks

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 3rd party may create such a utility.