Comtech EF Data RCS10 - Manual (Page 220)

Principles of Operation RCS10 Redundant Communication System
Page 5-4 TM058 - Rev. 2.3
BYTES 1 TO 15
DATA
120 BITS 1 2 3 4 5 6 7
BYTE 0
8
OVERHEAD
FRAME ALIGNMENT
BYTES 17 TO 31
DATA
120 BITS 1 2 3 4 5 6 7
BYTE 16
8
OVERHEAD
SIGNALLING
BYTES 33 TO 47
DATA
120 BITS 1 2 3 4 5 6 7
BYTE 32
8
OVERHEAD
HOUSEKEEPING
BYTES 49 TO 63
DATA
120 BITS 1 2 3 4 5 6 7
BYTE 48
8
OVERHEAD
SIGNALLING
SPARE
UNIQUE WORD
X 0 0 1 1 0 1 1 1
SEE NOTE 1 SEE NOTE 1
NOTES:
1. Bytes 16 and 48 are used for Signalling
bits or mapping bits at 1.544 Mbps and
above. They are used for "Enhanced"
mode ES - ES data in the DMD2400.
SPARE - Used in "Enhanced" mode.
SPARE - Used in "Enhanced" mode.
Not used in "Standard" mode
(Was IBS option encryption).
Used in "Enhanced" mode.
Multiframe
Message
Backward Alarm
ES to ES Communications
Channel. IBS "Standard"
mode.
IBS FRAME STRUCTURE
5.5.5.1 Standard IBS Mode
In the first or "Normal" mode, all bit assignments are per the IBS standard. The bits of Overhead
Housekeeping byte 32 are implemented as shown below:
Bit 1 - ES to ES Data Channel This bit is routed directly to the ES to ES Data Channel.
Its data rate is 1/512th of the aggregate rate (or 1/480
th of
the through terrestrial data rate), and is normally used
to super-sample an asynchronous data channel.
Bit 2 - Part of the Frame Alignment word.
Bit 3 - Backward Alarm Transmit and Receive with main processor to activate
main alarm/LED
Bit 4 - Multiframe Message As per IBS
Bits 5 and 6 - Spare Not currently Utilized
Bits 7 and 8 - Encryption Utilization Not currently Utilized
The ratio of the through terrestrial data channel rate to the aggregate rate is 15/16.
The standard transmit and receive channels of the ES to ES data channel in standard IBS mode are
raw channels operating at the specific bit rate as controlled by the data channel rate, without
buffering. Also no clocks are provided with this channel. Since it would be rare that the data rate
provided was exactly that required for a standard rate device, the only method of communicating
using this channel is to allow it to over-sample the user data. The ES to ES data channel rate
should normally then be a minimum of 3 times the desired asynchronous rate to work properly,
while 4 times the desired rate would have fewer errors.