Two families, one platform, and a decision that just got a lot more interesting. The SR series was always the economical entry point; the PR family was the expandable workhorse. Then the SR firmware update landed — V0.16 on the SR-12, V0.05 on the SR-12-B, SR-22 and SR-22-B — and quietly rewrote the rules of that comparison. The cheap side just gained a serious amount of muscle.
Let me walk you through what changed, what did not, and what that means for the machine you are building right now.
What the New Firmware Actually Delivered
Read the update list once, slowly, becuase each line is a spec-sheet change:
- APP blocks supported
- 512 FBD blocks; program memory expanded to 32K
- DC models gain 4-channel high-speed counting at 65 kHz — SR-12/SR-12-B on I5~I8, SR-22/SR-22-B on I9~IC
- A new AB encoder block, occupying terminals I5 and I6 exclusively, currently supported only by the SR-12DC-DA-R
- VB, VW and VD blocks added
- The SR-22DC-DA-R and SR-22DC-DA-R-B carry 256 AF blocks and 256 F blocks
That is not a bug-fix release. That is a product-line repositioning hiding behind a version number.
The Capacity Gap Just Shrunk
Here is the honest math before the update: SR-12 and SR-22 topped out at 256 function blocks, while the PR family ranged from 512 to 1024. For a project with analog loops and growing logic, the PR was the only real choice. After the update, the SR series runs 512 FBD blocks with 32K of program memory — the same class as the PR-12 and PR-14 territory. The ceiling did not vanish, but it moved, and it moved a lot.
That changes the selection conversation for a whole class of machines: pump sequences, HVAC fan controls, greenhouse logic, small packaging cells. If the program fits in 512 blocks — and most of them do — the SR is no longer the compromise pick. It is the right pick.
The High-Speed Counting Story
The quiet headline is the 65 kHz high-speed counting on the DC models. Four channels, on a budget controller. The SR-12 DC counts on I5 through I8; the SR-22 DC on I9 through IC. For encoder feedback, flow-meter pulses and production counting at speed, that capability used to mean moving up a product class. Now it sits inside the entry family.
And then there is the AB encoder block. It occupies I5 and I6 exclusively, and right now only the SR-12DC-DA-R supports it. A quadrature encoder on a nano-PLC is the kind of feature that makes a motion-oriented OEM stop and read the datasheet twice. The restriction is honest — one model, two terminals — but the capability is real, and it points where the family is heading.
Where PR Still Wins
Do not misread this as the PR family losing its reason to exist. The PR class still holds the top of the line: 1024 function blocks on the PR-18, PR-24 and PR-26, LCD-and-keypad operator interfaces, and the display-free PR-6 for series OEM work. The -N suffix models — the PR-12DC-DA-R-N and its siblings — push the mid-range to 1024 blocks too, with program memory expanded to 64K. The SR-22DC-DA-R now matches the PR-12/14 class on flags and analogs — 256 AF and 256 F blocks — but the big PR CPUs still out-muscle the whole SR line on sheer capacity.
The decision framework survives, sharpened: small relay-replacement and compact control jobs go SR; the machines that will grow, need a display, or demand maximum headroom still belong on PR. The middle ground — the zone where SR used to feel cramped — is now genuinely contested, and that is good news for your BOM.
Real Selection: Two Projects, Two Answers, New Math
Project one: a shower timer replacement — two inputs, one output, a 24-hour schedule. SR-12, minimum cost, never in doubt. Project two: a packaging cell with a small encoder for position and 40 I/O planned with expansion. Before the firmware, that went to a PR-26 without a second thought. After the update, the honest conversation includes the SR-12DC-DA-R — the AB encoder block, the 65 kHz counting, the 512 blocks — and the price gap bewteen the two answers is real money on a machine that ships in volume.
The right answer still depends on the expansion plan. The SR family expands, but the PR family expands further. A cell that will add modules next year still belongs on PR. A cell that is defined today fits SR — and fits well.
The Voltage and Interface Notes
Both series come in 12/24VDC and 110/240VAC versions; digital expansion modules mirror that choice; analog Expansions are 12/24VDC only. The SR display story stands: SR-12 and SR-22 default to LCD, the "-B" suffix strips it for bare-OEM use. The new firmware does not change the wiring book — it changes what the CPU can do with the signals once they arrive.
And the AB encoder note deserves a wiring warning: those two terminals are dedicated when the block is used. I5 and I6 are not free inputs anymore. Plan the I/O map with the encoder in mind before the schematic is drawn, not after.
The Verdict, Updated
Buy SR when the job is compact, the price is the point, and the new firmware's capacity covers the logic — it covers more than you think. Buy PR when the machine will grow, needs the LCD operator interface, or wants the 1024-block ceiling as insurance. Both are right tools; the line between them just moved, and the budget buyer is the one who benefits.
And when in doubt, price both. The gap is smaller than it was — and the SR side just got a lot harder to argue against.
