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Download a copy of the SEC-232m manual in: Rich Text Format Text Format The SEC-232m (picture) allows you to interface two high speed quadrature encoders and eight parallel I/O bits to a standard RS-232 port. The SEC-232m is contained in a very small 2.5" x 2" x .7" inch enclosure. It is designed to connect directly to a PC standard DB-25 serial connector. With wiring adapters any RS-232 serial port may be used.

How it works

Inside the small enclosure are two encoder interface chips, a microprocessor, a RS-232 driver chip, and a clock chip. The encoder interface chips handle the quadrature decoding and 16 bit up/down counting. The microprocessor monitors the two encoder chips and is programmed to extend the counters to 24 bits. The RS-232 driver chip generates the signals necessary for serial communication. The microprocessor has eight programmable input/output lines which are also monitored and related to the counts. The data is collected into packets and these packets are sent via RS-232 signals whenever the host computer requests data.

Host computer programming.

The SEC-232m is designed to produce 16 byte packets when the host computer requests data from it. These data packets are comprised of the two encoder counters, timer information*, input/output port data, and a CR/LF. The 16 byte packets are coded in Biased Binary which allows transfer of the data using all printable ASCII characters. The host computers task of data verification and decoding is greatly simplified by the use of Biased Binary data. All commands that the SEC-232m can recognize are single ASCII characters which can be sent at anytime in any order. All responses from the SEC-232m are in 16 byte packets, 14 data bytes followed with a carriage return and a linefeed. Packets containing currant counter and timer data are formed whenever a predetermined event occurs. Events can be data transitions on input pins or host commands. The packets are stored in a queue until the host computer polls for data. When a poll command is received the packets stored in the queue are sent in the order that they occurred. If there is no currently waiting packet, one is formed and sent with the currant counts and I/O port data at the time that the poll command was received.

SPECIFICATIONS

Interface:

The SEC-232m is designed to attach to any RS-232 serial port. The serial port connector is a male DB-25 wired to connect directly to a PC standard 25 pin serial connector. Appropriate wiring adaptors are available to allow connection to other RS-232 port standards.

Communications:

The SEC-232m communicates at 9600 baud with 8 data bits, 1 stop bit and no parity.

Commands:

The SEC-232m accepts single character commands in ASCII, some commands requre additional characters as parameters.

Response:

The SEC-232m when appropriate responds with a packet made up of 16 ASCII characters. There is buffer space for six packets. These 16 character packets are formatted in Biased Binary as follows.

XXXX YYYY TTTT MM crlf

Binary data is extracted from Biased Binary characters as follows: Start with a zero. For each new character, multiply the accumulated value by 64 (40h), add the new character, and then subtract 32 (20h). The resulting number will then need to be sign extended by checking if it is greater than 1/2 of the maximum count and if it is, subtracting the maximum count from it. The Multi Purpose number contains I/O data and flags reporting the status of the SEC-232m.

Encoder Inputs:

A pair of quadrature-encoded TTL-level signals for each of two counters.

Counter Size:

24 bit binary counters for each encoder and the TIMER*.

Counting Rate:

The standard unit has its digital input filter clocked at 4 MHz, which allows a input counting rate of up to 500 khz. Options are available for other counting rates.

Input \ Output:

8 total I/O lines programmable with host commands to be Input or Output. There are two data masking registers which are used to determine how the data bits are used. One register sets up Input or Output and the other determines which input bits will cause events that generate packets.

TIMER Data:

There is a free running counter who's value is transferred in each packet. This is useful for making velocity measurements and other requirements. *A command is available which converts this data to a third LOW speed (10khz) encoder input. Two of the INPUT pins are then dedicated to the third encoder.

Connectors:

DB-25 female connector for connection to the RS-232 port. A DB-25 male connector for connections to I/O pins, Encoder Signals and the Power Supply.

Power Supply:

A 300 ma 5 volt power supply is included with the SEC-232m. The SEC-232m requires 150 ma of power leaving 150 ma for encoders etc. Larger power supplies are available if needed.

Connector:

A DB-25 female connector & hood with power supply wired is supplied. Completely wired encoder cable assemblies are available as an extra cost option.

For more Information:

A copy of the technical manual containing a sample interface program written in Quick Basic is available. Call or write for pricing. Dealer inquiries are welcome.