Opto 22 SNAP PAC controllers and SNAP PAC brains serve some of the same functions in your SNAP PAC System, but they also differ.
This chart compares the features of the latest PACs and brains, with minimum firmware version R9.5 and PAC Project R9.6.
For more details, see the PDF, SNAP PAC Controller & Brain Comparison Chart.

	Software	Standalone PACs		Rack-mounted PACs		Ethernet Brains		Serial Brains
Feature	SoftPAC	SNAP-PAC-S1 SNAP-PAC-S1-FM	SNAP-PAC-S2	SNAP-PAC-R1 SNAP-PAC-R1-FM	SNAP-PAC-R2 SNAP-PAC-R2-FM	SNAP-PAC-EB1 SNAP-PAC-EB1-FM	SNAP-PAC-EB2 SNAP-PAC-EB2-FM	SNAP-PAC-SB1	SNAP-PAC-SB2
Runs PAC Control strategies	x	x	x	x	x
Max PAC Control charts running at once	64	32	32	16	16
Communication
Two independent Ethernet network interfaces (two IP addresses)	a	x	x	x	x
Two switched Ethernet network interfaces (one IP address) for multi-drop						x	x
Total number of RS-232 serial ports	b	2	4c	1	1	0	0	0	0
Total number of RS-485 serial ports	b	1	4c	0	0	0	0	1	1
Protocols
EtherNet/IP (Allen-Bradley RSLogix systems, others)		x	x	x	x	x	x
Modbus/TCP (slave)		x	x	x	x	x	x
OPC driver support	x	x	x	x	x	x	x
RESTful API		x	x	x	x
HTTP/HTTPS		x	x	x	x
OptoMMP memory-mapped protocol	xd	x	x	x	x	x	x	x	x
SNMP		x	x	x	x
FTP server, file system		x	x	x	x	x	x
FTP client	x	x	x	x	x
SMTP (email client, authentication, attachments	x	x	x	x	x
Direct access to hard drive, network drives (Dropbox, etc.)	x
Realtime clock	a	x	x	x	x	x	x	x	x
Backup battery (recharges when device has power)		x	x	x	x	x	x	x	x
Physical RAM (MB) RAM available for PAC Control strategy (MB) Battery-backed RAM (MB) Flash memory (MB)	-a 64 8 -e	32 16 8 16	32 16 8 16	16 4 2 ​8	16 4 2 ​8	16 -- -- 8	16 -- -- 8	16 -- -- 8	16 -- -- 8
Removable data storage (microSD card slot)	a	32 GB max	32 GB max	32 GB max	32 GB max
32-bit processor	a	x	x	x	x	x	x	x	x
Floating-point unit (FPU)	a	x	x	x	x
Power requirements	a	8-32 VDC 10W-11.3 W max		5.0 to 5.2 VDC @ 1.2 to 1.5 A		5.0 to 5.2 VDC @ 750 mA-1.0 A		5.0 to 5.2 VDC ​@ 750 mA-1.0 A
Operating temperature (degrees C) Storage temperature (degrees C)	a	-20 to 60 -40 to 85		-20 to 60 ​-40 to 85		-20 to 60 ​-40 to 85		-20 to 60 ​-40 to 85
Humidity (non-condensing)	a	0-95%		0-95%		0-95%		0-95%
PID logic (maximum 96 PID loops per controller or brain)				x	x	x	x	x	x
Digital I/O features
Input latching				x	x	x	x	x	x
On/off status				x	x	x	x	x	x
Watchdog timer				x	x	x	x	x	x
High-speed counting (up to 20 kHz)f				x		x		x
Quadrature countingg				x		x		x
On-pulse and off-pulse measurementf				x		x		x
Frequency and Period measurementf				x		x		x
TPO (time-proportional output)				x	x	x	x	x	x
Digital totalizingf				x	x	x	x	x	x
Pulse generation (continuous square wave, N pulses, on-pulse, off-pulse)				x	x	x	x	x	x
Analog I/O features
Thermocouple linearization (32-bit floating point for linearized values)				x	x	x	x	x	x
Minimum/maximum values				x	x	x	x	x	x
Offset and gain				x	x	x	x	x	x
Scaling				x	x	x	x	x	x
TPO (time-proportional output)h				x	x	x	x	x	x
Output clamping				x	x	x	x	x	x
Filter weight				x	x	x	x	x	x
Watchdog timer				x	x	x	x	x	x
Analog totalizingi				x	x	x	x	x	x
Rampingi				x	x	x	x	x	x
a As provided by the Microsoft Windows computer SoftPAC runs on. b SoftPAC cannot communicate through serial ports on the PC. c Serial ports are software configurable for RS-232 or RS-485. d SoftPAC includes Status Read, Status Write, and Scratch Pad memory map areas. e Flash memory function implemented via a file; size is limited only by disk space. f Four-channel modules only; not on high-density digital modules. g Requires a SNAP-IDC5Q quadrature input module. h Requires a SNAP analog TPO module (SNAP-AOD-29). i Requires a SNAP PAC controller and PAC Control commands.