Data Port End-To-End Delay; Response Times And Buffer Space - PictureTel Concorde 4500 Servicing Manual

CONTROL AND DATA PORT COMMUNICATIONS
Data Port End-to-
End Delay
Response Times
and Buffer Space
D-4
peripheral devices support baud rates in increments such as 300,
600, 1200, 2400, 4800, 9600, or 38.4 baud.
The Concorde¥4500 introduces a certain amount of end-to-end
transmission delay.
End-to end transmission delay is due to the following factors:
Buffering (especially with synchronous communication)
Multiplexing (since data may accumulate for up to an entire
frame before being transmitted)
In certain applications, the effects of end-to-end delay may be
minimized by one of the following tasks:
Transmitting larger data packets, if the application requires
acknowledgment for each packet.
Permitting more than one outstanding acknowledgment.
The Concorde¥4500 responds to the RTS signal and the DTR signal
from the DTE as follows:
The CTS signal responds to a change in the state of the RTS
signal within 15 milliseconds.
The DSR signal responds to the DTR signal within
15 milliseconds.
When the Concorde¥4500 input buffer space nears its capacity to
accept incoming data from a DTE device, the Concorde¥4500
deasserts the CTS signal, notifying the DTE to stop sending data.
The exact amount of buffer space remaining once the
Concorde¥4500 deasserts the CTS signal depends on the particular
port. Control port B has 256 bytes of available buffer space.
When the Concorde¥4500 deasserts the CTS signal, the maximum
safe response time for the DTE device to prevent loss of data
depends on the baud rate being used. Devices with lower baud rates
can have longer response times than devices with higher baud rates.