P300H
P300 Series Modem Installation and Operating Handbook
Page 148
8.6 DETERMINING EXACT MAXIMUM ESC BAUD RATES
Should you wish to determine the exact maximum ESC Baud rates, in order to change the overhead
allocation to achieve specific ESC rates with specific overheads, then the following section may be
useful.
For
Standard IBS
the
exact
maximum continuous rate is:
Baud Rate = (Main data rate/15) x (O/H bits allocated/32) x (Bauds per Character/9)
Where:
Main data rate:
The main modem data rate, eg 64000bps (/15 gives total overhead)
O/H bits allocated:
The number of bits of the overhead allocated to the ESC, for example if
the ESC is set in P230 mode, then 20 bits (TS16 bits 1-8, TS48 bits 1-
8 & TS32 bits 4-8) are available (/32 give the proportion of the
overhead allocated to the ESC)
Bauds per Character:
The number of Baud periods per character (eg for async character
format 8,N there are 10 Baud periods per character: start + 8 data bits
+ stop (/9 as 9
synchronous
bits are always used for each character).
Note that if the CAS Multiframe is active
to transfer G.732 CAS
, then TS16 and TS48 are not available.
Note also that is the CAS Multiframe is active
without
CAS, ie to maintain the timeslot ID for an `Odd
value of N` or if RBS signalling is active, then only 7 out of 8 of every TS16 are available for ESC, as
TS16 has to carry the `CAS MF unique word` or `pack byte` every 8th frame. In this case simply
consider TS16 as providing 7 bits of overhead not 8.
For
Custom IBS
modes this is unchanged unless Minimum Overhead mode is selected, in which case
the overhead will
vary up or down from the standard 1/15th to accommodate whatever Baud rate
is set on the ESC Rate screen.
In all
IDR modes
, the ESC channel is an 8kbps synchronous channel, and if the ESC port is set to
provide an async interface the
exact
maximum continuous async rate is:
Baud Rate = 8000 x (Bauds per Character/9)
Where "Bauds per Character" is the number of Baud periods per character (eg for async character
format 8,N there are 10 Baud periods per character: start + 8 data bits + stop (/9 as 9
synchronous
bits
are always used for each character). This results in a maximum of 9777Baud with 11 Baud periods per
character (eg start + 8 + stop), and 8888 Baud with 10 Baud periods per character (eg start + 8
+ stop), as used with Paradise & SA-bus M&C protocols (SA-bus is start + 7 + stop = 10 Baud
periods per character). So when set for [8 bits No Parity] or [7 bits with Parity] the maximum standard
Baud rate is 4800 Baud. When set for [8 bits with Parity] the maximum standard Baud rate is 9600 Baud.
