I. Model and Positioning

Model: JANCD-MB21 (commonly Rev C, part number DF8101357, different from MB20)

Series: JANCD → J300 (numerical control) / RK20 (robot)

Evolution: MB20 (A/B/C/E) → MB21 (independent second generation, not a revised version of MB20)

Status: Original factory has completely discontinued production, no replacement model available, belongs to high-value spare parts.

II. Core Differences between MB21 and MB20E (Key Points)

1. Hardware Architecture Upgrade

Slots: MB21 has 8 slots (MB20 has 6 slots), supporting more expansion daughter boards.

Bus: MB21 is an upgraded dedicated bus, with a bandwidth increase of 40% and stronger anti-interference.

Power Supply: MB21 has 24V with a load capacity of 300mA (MB20E has 200mA), dual redundant + overcurrent protection.

Size: MB21 is approximately 280×250×35mm (about one circle larger than MB20), weight 3.2kg.

2. Compatibility (Important)

Incompatible with MB20 daughter boards: The slot definitions of MB21 are different from MB20, PC20/MM20/JIF10/JSPxx cannot be inserted interchangeably.

Exclusive daughter boards: MB21 is equipped with PC21 (CPU), MM21 (memory), JIF21 (communication), JSP21 (spindle), etc.

System Adaptation: Only applicable to later models of J300 and RK20 robot control cabinets, cannot be directly replaced by MB20.

3. Reliability and Alarm

Temperature Range: 0–60℃ (MB20E is 0–55℃), suitable for harsh working conditions.

MTBF: Approximately 150,000 hours (MB20E is 120,000 hours).

Common Alarms: ALM01 (bus error), ALM02 (battery low) occur at a rate much lower than MB20.

III. Technical Parameters (MB21)

Power Supply: DC24V ±10%, power consumption approximately 70W.

Backplane Slots: 8 (CPU / memory / communication / spindle ×3 / reserved ×2).

Interfaces: CN1 (24V), CN2 (5.5V battery), CN3 (MDI), CN4 (RS-232C), CN5 (I/O), CN6–CN9 (extension).

Battery: NEC 5.5V lithium battery (life 3–5 years, compatible with MB20).

PCB Printing: JANCD-MB21, Rev A/B/C (C version is the most stable).

IV. Comparison Overview of MB20 and MB21 Table

Project MB20E (Final Version) MB21 (Second Generation)

Number of slots 6 8

24V load capacity 200mA 300mA

Sub-board compatibility PC20/MM20, etc. PC21/MM21, etc. (cannot be inserted interchangeably)

Temperature range 0–55℃ 0–60℃

MTBF 120,000 hours 150,000 hours

Replaceability Replaceable with MB20A/B/C Not replaceable with MB20, exclusive system

V. Typical Configuration Combinations

Numerical Control J300 (Later Version): MB21 + PC21 + MM21 + JIF21 + JSP21 (Spindle)

Robot RK20: MB21 + PC21 + MM21 + JIF21 + Axis Card

VI. Replacement and Selection Suggestions

MB21 and MB20 are completely incompatible: Cannot be directly replaced; the entire sub-board needs to be replaced.

Priority of spare parts: MB21 has fewer in stock and higher price; prefer to select C version with OK test result and warranty.

Alarm handling: ALM01 checks if the sub-board is inserted tightly and the gold fingers; ALM02 replaces the 5.5V lithium battery.