DS200MBHAG2A | GE Surplus Stock

Description

Product Introduction

The DS200MBHAG2A is the top-tier Modbus gateway for GE’s Mark V turbine platform. The G1A choked when you needed two separate SCADA systems pulling different data sets. This board runs two independent Modbus masters simultaneously without breaking a sweat.

What justifies the “G2” designation? Three major upgrades. First, the processor jumps from a 40MHz C167CR to a 66MHz C167CS. Second, RAM doubles to 2MB—enough to actively map 8,000 registers at 25ms. Third, and most important, the board has two completely independent Modbus state machines. You can configure Port 1 as a master polling 32 downstream devices while Port 2 acts as a second master polling a different set of 32 devices. The G1A couldn’t do that—it forced you into master/slave or slave/slave configurations. To be frank, if you have two control rooms or a dual-redundant SCADA setup, the G2A is the only choice.

Key Technical Specifications

Compatible Replacement Models

✅ Drop-in Replacement: DS200MBHAG1A
Slower processor, half the RAM, single master mode only. Same pinout. Swaps directly, but you lose dual master capability. If your application uses Port 2 as a second master, the G1A will ignore that configuration. Your second SCADA will get no data.

⚠️ Software Compatible: DS200MBHAG2
Original G2 release with 66MHz processor but only 1MB RAM. Requires a firmware flash to enable the full 8,000 active register mapping. Estimate 90 minutes per board including verification. The G2 also lacks the G2A’s improved thermal management—runs about 8°C hotter at full load.

❌ Hardware Incompatible: DS200MBHAG1 (any variant)
Different backplane interrupt assignment. The G2A uses IRQ level 5 on the VME bus. The G1 series uses IRQ level 3. Putting a G2A into a rack configured for G1 interrupts will cause bus contention and random resets. You can reconfigure the rack’s interrupt jumper (J3 on the CPU board), but that affects all slots. Consult your system integrator before mixing G1 and G2 boards.

Frequently Asked Questions (FAQ)

Can I run both ports as Modbus masters polling different baud rates?
Yes. That’s the whole point of the G2A. Port 1 can poll at 9600 baud to an old RTU while Port 2 polls at 115200 baud to a modern PLC. Each port has its own timing engine. The only limit is total CPU load—polling 32 devices on both ports simultaneously uses about 70% of the 66MHz processor. The remaining 30% handles the VME backplane and register mapping.

How do I verify dual master mode is actually working?
Put an oscilloscope on both TX lines simultaneously. In dual master mode, you’ll see independent asynchronous traffic. If you see packets on Port 1, then a gap, then packets on Port 2, the board is actually time-slicing (single master mode). Genuine dual master shows packets overlapping—the board has two separate UARTs. The G2A uses a dual UART chip (Exar XR16L788). The G1A uses a single UART with a multiplexer.

My G2A shows the ERR LED flashing six times, pausing. What’s the fault?
Six flashes means “dual master collision.” The board attempted to transmit on both ports simultaneously, but the backplane DMA controller couldn’t keep up. This usually happens when you’ve mapped more than 6,000 active registers AND you’re polling both ports at maximum speed. Reduce your active register count to 5,000 or lower your poll rate on one port. If the problem persists, replace the board—the DMA controller may be failing.

What’s the maximum number of Modbus slaves per port?
Officially 32 per port, 64 total. Unofficially, we’ve run 48 slaves on Port 1 and 16 on Port 2 without issues. The practical limit is scan time. Each additional slave adds about 15ms to the poll cycle (assuming three registers per slave). 64 slaves at 15ms each gives you a 960ms scan—too slow for anything but annunciation. Keep it under 24 slaves per port for sub-500ms response.

Can I upgrade a G1A to G2A specifications by swapping the processor and RAM?
No. The G1A PCB lacks the trace routing for the C167CS’s additional address lines and the dual UART chip. You’d need to replace about 30 components and add 15 pull-up resistors. To be frank, we’ve never seen a successful field upgrade. The one shop that attempted it cooked three boards before giving up. Buy the G2A.

How do I store a spare DS200MBHAG2A for long-term backup?
Original anti-static bag, flat storage, 15-25°C. The board has a supercapacitor (C102, 0.22F) instead of a battery for the real-time clock. Supercaps last about 10 years on the shelf versus 8 years for a lithium battery. However, supercaps degrade faster at high temperatures. Store below 25°C. Every two years, power up the board for 24 hours to reform the supercap. If you skip this and store it for five years, expect the clock to lose about 4 hours per day until the cap reforms.

What’s the typical failure mode on the G2A?
The voltage regulator for the 3.3V rail (U5, a Linear LT1764) runs hot—about 65°C at full load. After about 40,000 hours, the regulator’s output starts sagging below 3.25V. Symptoms: random resets, corrupted Modbus frames, or the processor locking up. Measure TP3 (3.3V test point). If you see less than 3.25V with the board at operating temperature, replace U5. It’s a 5-pin DDPAK, about 20 minutes with a hot air station. We sell the replacement regulator for $12.

Do you offer any configuration migration service from G1A to G2A?
Yes. Export your G1A configuration using the MBHAG_Config tool (produces a .MBG file). We’ll convert it to G2A format and expand your register map to use the additional memory. Cost is $250 per conversion, includes verification on our test rack. Turnaround is two business days. Without conversion, you’ll need to manually rebuild your register map in the G2A tool—expect 4-6 hours for a typical 2,000-register map.

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