Appendix
IM-1004 | REV181127
Page 29
©2018 Celera Motion
Mercury II 6000 Series Encoders
Sensor Installation Manual and Reference Guide
7.5
Serial Interface Specifications
Introduction
The serial interface to the Mercury II 6800Si/Pa allows a serial host (controller) to receive position
and status information serially from the sensor. Serial communications between the encoder and
controller permit high speed motion system operation with high encoder resolution: up to 10 m/s at
resolution of 1.22 nm. The serial data word consists of the following sequence:
Position word of four start bits
Four to thirty-five position bits
Nine bits of status
Six-bit Cyclic Redundancy Check (CRC) to provide error detection
Four
stop
bits
The encoder’s position is sampled by the MII6800Si at the moment the host commands a sample
(falling edge of nCS); the only latency in the system is the time required for the host to receive the
position word. This architecture minimizes latency and eliminates jitter due to sampling
uncertainty.
Serial Interface Input/Output
MII6800Si (Serial Interface)
Pin Name
Direction
Description
14 SD OUTPUT
Serial
Data from Sensor to Host
6 SDATA_OUT- OUTPUT
Serial
Data from Sensor to Host
13
SCL
OUTPUT Serial Clock from Sensor to Host
5
SCLOCK_OUT-
OUTPUT
Serial Clock from Sensor to Host
10 SC INPUT
Serial Clock from Host to Sensor
11 SCLOCK_IN- INPUT
Serial Clock from Host to Sensor
1 nCS+
INPUT
Chip Select from Host to Sensor
3 nCS-
INPUT
Chip Select from Host to Sensor (Negative True to start capture)
7,8 +5V
2,9 GND
15
Alarm
OUTPUT
For low level or saturated signal
4
Reserved
Do Not Connect
12
Reserved
Do Not Connect
MII6800Pa (Panasonic)
The following are the pins used by the MII6800Pa Panasonic serial interface.
Pins 2, 7, 8, 9 are the same for both MII6800Si and Panasonic
Pins 10 and 11 are different for Panasonic
All other pins for Pa are not connected (NC)
Pin Name
Direction
Description
10 Input/Output
Request for Serial Data from Host to Sensor
11 REQ_SD- Input/Output
Request for Serial Data from Host to Sensor
7,8 +5V
Input
2,9 GND
Input
