PCC-IV Instruction Manual (rev. 0.2)
Page 5-5
Section 5 – Configuring Blockware
Any value that needs to be established when the controller is first configured or those values that the user will
change rarely are parameters. In Section 6, the purpose of each function’s parameter will be identified in detail.
Parameters are referred to by their name or by “P1”, “P2”, etc.
Analog
Block outputs within the PCC-IV that can be varied continuously and in small increments are called analog values.
Analog values inside the PCC-IV are normally considered to be 0.00%-100.00% values. However, analog block
outputs can range from -327.67% to +327.67%, and all computations are carried out to 0.001% internal resolution.
Discrete
Block outputs within the PCC-IV that can only have values of 0 or 1 (i.e. ON / OFF, TRUE / FALSE, HI / LOW) are
called discrete values. Discrete and analog values cannot be intermixed. That is, if a function type calls for one of
its inputs to be an analog value, then the user cannot assign discrete value to this input.
NAND
NAND flash memory is the permanent memory that stores all the firmware (i.e., non-changeable software) that
makes the PCC-IV work (like ROM except that it can be re-flashed). This memory is not lost when the power is
turned off. The PCC-IV screen driver firmware, menus, Modbus protocol, version number, Ethernet and RS485
drivers, etc. are stored in NAND flash memory.
RAM
RAM stands for
R
andom
A
ccess
M
emory. RAM can be read from and written to. RAM is volatile, temporary memory
that is erased every time power is lost. The advantage is that is it very fast. RAM is where the configuration
blockware is processed during normal operation.
EEPROM
EEPROM, or Electrically Erasable/Programmable Read Only Memory, is also flashable. The block function-types,
softwiring, parameters, communication setup, calibration data, etc. are stored in this flash memory.
Upon power-up, the PCC-IV copies the contents of the EEPROM to RAM. The controller then operates from this
RAM. When a user presses the “Save Config Changes” soft-button via the Utilities >> Memory submenu, the
applicable contents of NVRAM (see below) are copied to EEPROM for additional redundancy.
NVRAM Retentive Memory
NVRAM, or Non-Volatile RAM, is used to automatically save and restore specific block parameters and specific
block output values at the end of each 100ms “scan”. NVRAM retains its data after being powered down for
approximately 20 years. NVRAM does not use batteries, or capacitors, to retain its data, and can be written
indefinitely without wearing out. PCC-IV has dual redundant NVRAM chips and alternates writes to chip A vs chip
B every other scan.
Typically, setpoints, ratios, flow totals, and pushbutton statuses are saved and restored to/from retentive memory.
Retentive memory allows a controller to resume controlling in the same state following power up as it was prior to
shutdown. The block outputs and block parameters that are saved in retentive memory are specified in Section 6.
Some of the functions that save outputs to and are restored from retentive memory are:
FPT/H (Front Panel Track and Hold), F(T) (Function of Time ramp generator), FPCON (Front Panel Constant),
COUNT (Pulse Counter), RDIN (Remote Discrete Input), PB (Pushbutton), and F/F (Flip/Flop). Most other function
type outputs are re-calculated every scan based on the current inputs and are not restored at power up.
A5 Core
This is the core (microprocessor) that controls communication with any external device (Modbus, USB
programming, front panel).
M4 Core
This is the core (microprocessor) that controls the Watchdog Timer, Real Time Clock, all internal processes, and
I/O that uses the Motherboard and Option Boards (AIN, ZAIN, AOUT, DIN, ROUT, TOUT, DOUT).
