Composite Rates 4.8 - 32Kbps
2 x 24 Bytes at 19.2Kbps
S
1
DDDDDDDDDDDDDDDDDDDDDDD
C
1
DDDDDDDDDDDDDDDDDDDDDDD
S
1
Synchronising byte
C
1
Configuration byte
D
Data Byte
Synchronisation
Synchronisation will occur after receipt of a superframe, i.e. 80ms, irrespective of the
composite data rate. A super-frame comprises four composite frames, each of which has a
different sync character.
Composite Link Rates
The composite data rate can be selected in increments of 800bps from 4.8Kbps to 64Kbps.
This allows most efficient use of data bandwidth if multiplexers are daisy chained.
Round Trip Polling Delay
Round trip delay is defined as the time interval which elapses when a "poll" from a computer
is transmitted from one of the low speed data ports of the multiplexer, through the composite
link, and then looped at the remote multiplexer to return to the computer. This is generally
referenced when the computer data is transmitted through a 9.6Kbps channel. The Sprint 2
has a delay of only 12ms at all link rates.
Interface Signals/Sample Rate
The Sprint 2 units sample and transmit the RTS and DTR signals from all 4 or 8 channels
approximately every 230ms via the configuration bytes. If the full data bandwidth is not
allocated, the residual is used to pass the interface signals, reducing delay to less than 15ms
(800bps residual) or 10ms (>2400bps residual) respectively.
Therefore if the requirement is for onward linked, half duplex communication it is essential
to leave some bandwidth unused to speed up the interchange of control signals. If the IBM
Bisync protocol is being transmitted it is recommended that 2.4Kbps of data bandwidth is
unused.
