Command Block Format - Alesis ADAT-M20 Supplementary Manual

COMMAND BLOCK FORMAT

The definition of CONTROLLER and DEVICE throughout this document shall be as follows:
"CONTROLLER" refers to the unit which controls the VTR.
"DEVICE" refers to the unit (VTR) which is controlled.
The communication between the CONTROLLER and DEVICE is composed of the following:
MSD LSD
Data
Cmd 1 Count Cmd 2
1 Byte 1 Byte
When the is zero, the
Data Count
inserted between and
Cmd 2
Cmd 1
Cmd 1 classifies the COMMAND into main groups which indicate the Function and Direction of the data to
follow.
CMD 1
0
1
2
4
6
7
Data Count
Data Count indicates the number of data bytes added following Cmd 2. It ranges from 0 to F.
Cmd 2
Cmd 2 is the designated COMMAND sent to the DEVICE or returned from the DEVICE.
Data
The number of data bytes and the content is defined by the specific Cmd 2.
Checksum
The Checksum is the sum of all bytes in the message, from Cmd 1/Data Count to the last byte before the
Checksum. The Checksum is used to verify data accuracy and reject communication sequences that contain bit
errors.
Alesis M20 RS-422 Document .................................................................................Page 3
Data -1
1 Byte
is not transmitted. When it is not zero, the
Data
.
Checksum
FUNCTION
System Control
System Control Return
Transport Control
Preset & Select Control
Sense Request
Sense Return
Data-n Checksum
(n = max 15)
1 Byte 1 Byte
corresponding to the value is
Data
DIRECTION
CONTROLLER DEVICE