Allen-Bradley MicroLogix 1400 User Manual

Publication 1766-RM001A-EN-P - October 2008
238 Application Specific Instructions
The RHC instruction provides a high performance timestamp for
diagnostics and calculation such as velocity. The controller maintains a 10
µs long integer free running clock/counter. This 32 bit value increments
every 10 µs after power-up
Enter the following parameters when programming this instruction:
• Destination is the address to store the current value of the 10 µs free
running clock. It can be an integer address, long integer address or
Float address.
Instruction Operation
This instruction executes on a true rung. When the rung is true, this
instruction moves the current value of the 10 µs free running clock into
the Destination.
If the Destination is an integer address type, only 16 bits are moved into
the address. If the Destination is floating point address, the long integer
value is converted into a float and is moved the relative address.
After the free running clock reaches 0xFFFFFFFF (42949.67295 seconds)
value, it wraps around to 0 and continues incrementing. The RESET signal
or Power Cycle sets the free running clock to 0.
RHC Instruction Valid Addressing Modes and File Types
For definitions of the terms used in this table see Using the Instruction Descriptions on page 92.
Parameter
Data Files
Function Files
(1)
CS - Comms IOS - I/O DLS - Data Log
(2)
Address Mode
(3)
Address Level
O I S B T, C, R N F ST L MG, PD RI/RIX PLS RTC HSC PTOX, PWMX STI EII BHI MMI LCD Direct Indirect Immediate Int16 Immediate Int32 Immediate Float Bit Word Double Word Element Float
Destination • • • •
(1) PTOX and PWMX files are only for use with MicroLogix 1400 BXB or BXBA unit.
(2) The Data Log Status file can only be used for the following math instructions: ADD, SUB, MUL, DIV, NEG, and SCP.
(3) See Important note about indirect addressing.
IMPORTANT
You cannot use indirect addressing with: S, MG, PD, RTC, HSC, PTOX,
PWMX, STI, EII, BHI, MMI, CS, IOS, and DLS files.
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Allen-Bradley MicroLogix 1400 Specifications

General

Processor	32-bit
Expansion Modules	Up to 7 expansion I/O modules
Power Supply	24V DC or 120/240V AC
Programming Software	RSLogix 500
Communication Ports	Ethernet, RS-232/RS-485 combo port
Controller Type	Programmable Logic Controller (PLC)
Series	MicroLogix
Digital Outputs	12
Analog Inputs	6 (embedded)
Analog Outputs	2 (embedded)
High-Speed Counter	6 high-speed counters
Pulse Output	2 (embedded)
Ethernet Port	Yes