A20B-8100-0662 Fanuc PCB Board A20B81000662 A2OB-8IOO-O662

FANUC A20B-8100-0662 | Series 21i-B Control Main CPU PCB — PMC-SA1, Without Ethernet, A20B-8100 Series, LCD-Mounted, For 21i-MB / 21i-TB, Japan Origin

Part Number: A20B-8100-0662

Manufacturer: FANUC Corporation (Japan)

Product Category: PCB — Main CPU Board (CNC Control Motherboard)

Series: A20B-8100 — FANUC 16i-B / 18i-B / 21i-B main board family

Overview

The FANUC A20B-8100-0662 is the main CPU board for FANUC Series 21i-B CNC controllers configured with PMC-SA1 and without embedded Ethernet.

It is the specific motherboard variant that defines the 21i-B system's feature set for this configuration: a capable, cost-effective CNC controller covering lathe (21i-TB) and machining centre (21i-MB) applications suited to the mid-range of machine tool complexity.

Within the A20B-8100-066x main board family, each part number corresponds to a specific combination of CNC series designation and on-board feature configuration. The -0662 is the baseline 21i-B board: PMC-SA1, without Ethernet.

The PMC-SA1 designation refers to the PMC (Programmable Machine Controller) specification — SA1 is the entry-level PMC within the 21i-B generation, handling typical machine ladder logic without the advanced programming capacity of the SB7 variant.

The absence of embedded Ethernet is the other defining characteristic: machines that require factory network connectivity must add an external Ethernet option board, while machines communicating only via RS-232C or PCMCIA operate with this board as standard.

The 21i-B series is FANUC's mainstream CNC for general-purpose production machine tools. It brings the same FSSB digital servo architecture and serial spindle interface as the higher 16i-B and 18i-B, within an axis count and PMC specification appropriate for typical 2 to 4 axis machine tools.

Key Specifications

The 21i-B in the 16i-B / 18i-B / 21i-B Generation

The A20B-8100-066x family covers the entire second-generation i-series across three CNC designations:

The 21i-B occupies the lower position in this generation's axis and function hierarchy. The 16i-B and 18i-B support more controlled axes and a wider range of advanced machining functions.

The 21i-B is matched to machine tools where 2 to 4 axes and standard cycle functionality meet all machining requirements — which describes the majority of conventional lathes, vertical machining centres, and drilling machines in global production.

A notable hardware difference is the CPU module. The 21i-B uses lower-specification CPU processors compared to the 16i-B and 18i-B.

The 21i-B's processing requirements are proportionally lower — fewer axes, simpler part programmes, less concurrent processing demand — so the reduced CPU specification is appropriate and does not limit practical machine performance.

PMC-SA1 — What It Means in Practice

The PMC (Programmable Machine Controller) in a FANUC CNC is the built-in PLC. It executes the machine builder's ladder logic handling all machine I/O: limit switches, door interlocks, coolant, tool changers, pallet systems, and everything outside direct servo and spindle control.

PMC-SA1 is the entry-level PMC specification in the 21i-B generation:

Programme steps: SA1 supports a defined number of ladder steps — sufficient for standard 2-axis lathe or 3-axis machining centre PMC requirements.

Ladder symbols: SA1 provides the standard set of relay contacts, coils, timers, counters, and comparison functions used in conventional machine tool ladder logic.

Execution speed: SA1 executes at the rate required for normal machine I/O response, adequate for spindle, coolant, door, and tool functions with response times in the tens of milliseconds.

For machines with complex tool changers, multi-pallet systems, or extensive user macro interfaces, PMC-SB7 (available on the -0663 and -0665 boards) offers more programme steps and expanded capability.

The -0662's SA1 serves the majority of standard machine tool applications without limitation.

FAQ

Q1: A 21i-B machine has a -0662 board (PMC-SA1, no Ethernet). Can it be replaced with the -0664 (PMC-SA1, with Ethernet)?

Physically and electrically, the -0664 can replace the -0662. The PMC specification is identical (SA1), so the existing PMC ladder transfers without modification.

The only difference is that the -0664 adds embedded Ethernet capability the -0662 lacks — the Ethernet port simply goes unused if not connected. 

Confirm the FROM software edition on the replacement board's modules is compatible with the specific machine configuration before substituting.

Q2: After installing a replacement A20B-8100-0662, the 21i-B shows PMC alarm ER01 (programme not found). What caused this?

PMC alarm ER01 indicates the PMC ladder programme is not present in SRAM.

Either the SRAM backup was not restored after replacement, the SRAM module was not transferred from the original board, or the restore process did not complete. Confirm the SRAM module from the original board is installed in the new board. 

Then restore the SRAM backup from the backup medium. If no backup exists, the PMC ladder must be reloaded from the machine builder's original programme files.

Q3: The 21i-B machine does not need Ethernet. If a -0664 board is used as a replacement, does unused Ethernet cause any problems?

No. The embedded Ethernet port on the -0664 is inactive if no cable is connected and no Ethernet parameters are configured.

It does not consume system resources or affect CNC performance.

The substitution is functionally transparent for machines that do not use Ethernet.

Q4: What axis control card is required on the A20B-8100-0662 for a 4-axis machining centre?

The A20B-3300-0032 (4-axis servo control card, Series 90B0 servo software) is the correct card for a 4-axis 21i-B configuration.

The A20B-3300-0033 handles 2-axis configurations. Always verify which axis card is fitted to the original machine before ordering a replacement — the axis card transfers with the other modules when the main board is replaced.

Q5: Is the DRAM module for the A20B-8100-0662 the same as for the 16i-B or 18i-B main boards?

No. The 21i-B uses different DRAM modules from those used on the 16i-B and 18i-B. The 21i-B (without Ethernet) uses A20B-3300-0291 (16MB DRAM) or A20B-3300-0290 (32MB DRAM).

The 16i-B and 18i-B use A20B-3300-0310 (16MB) or A20B-3300-0311 (32MB). 

Fitting a 16i/18i DRAM module to a 21i-B main board causes boot failure. Always confirm the correct module for the specific CNC designation.