Interface Overview - Datavideo HDR-200 User Manual

1. Interface Overview

Conforming to EIA RS-422A.

Full duplex communications channel is utilized.

Data is transmitted asynchronously, bit serial, word serial with data exchange between devices.

Standard transmission rate on the interface bus is 38400 bits per seconds (bps)

The data word utilized by the interface system is as follows :

D0
START
BIT
谐
1 Start bit + 8 Data bits + 1 Parity bit + 1 Stop bit. Odd Parity

ODD parity : The total of "1"s in D0+D1+ . . . D7+PARITY equals an odd number.
2. Command Block Format
The data communication is composed of the CMD-1/DATA COUNT byte, the CMD-2 byte, optional DATA bytes and
the CHECKSUM byte. Commands are transmitted in order from the MSB (Most Significant Byte) to the LSB (Least
Significant Byte). This means that when using the examples in this manual, the order in which the bytes are read is the
same order in which they are transmitted. When the DATA COUNT nibble is 0, no DATA bytes are transmitted or
required (the CMD-1/DATA COUNT byte, CMD-2 byte and CHECKSUM byte are still transmitted). When the
DATA COUNT nibble is not 0, the number of DATA bytes transmitted must correspond with the DATA COUNT.
These bytes are inserted between the CMD-2 byte and CHECKSUM byte.
COMMAND BLOCK FORMAT
The data communication between the controller and the device is performed as follows:
Name CMD-1
Nibble MSN
Size 1 Byte
1. MSN stands for Most Significant Nibble (4 bits)
2. LSN stands for Least Significant Nibble (4 bits)
COMMAND CONTENTS
CMD-1:
This is the first (Most Significant) nibble of the first byte of the command. The DATA COUNT (below)
fills the lower (Least Significant) nibble. It indicates the command or return group to which the command
belongs as per the table below
CMD-1
0x System Control
1x System Control Return
2x Transport Control
4x Preset And Select Control
6x Sense Request
7x Sense Return
Ex DVR Control
Fx DVR Return
HDR-200 RS-422 Protocol Reference V1.0
D1 D2 D3 D4
Data Count
LSN
1 Byte
Function
D5 D6 D7 PARITY
(ODD)
CMD-2 Data 0~15
(per Data Count)
0..15 Byte(s)
23
STOP
BIT
Checksum
1 Byte
Initiator
Controller
Device (HDR-200)
Controller
Controller
Controller
Device (HDR-200)
Controller
Device (HDR-200)