Command Response Time - Omega CN63100 Series User Manual

Figure 36, Character Frame
To allow the host adequate time to release the bus after a transmission, the
response time of the controller is programmable. The controller utilizes a
receiver design that interprets a mark condition for open connections.
Start Bit and Data Bits
Data transmission always begins with the start bit. The start bit signals the
receiving device to prepare for reception of data. One bit period later, the
least significant bit of the ASCII encoded character is transmitted, followed
by the remaining data bits. The receiving device then reads each bit position
as it is transmitted. Since the sending and receiving devices operate at the
same transmission speed (baud rate), the data is read without timing errors.
Parity Bit
After the data bits, the parity bit is sent. The transmitter sets the parity bit to
a zero or a one, so that the total number of ones contained in the transmission
(including the parity bit itself) is either even or odd. This bit is used by the
receiver to detect one bit errors occurring in the transmission. Given this
limitation, the parity bit is often ignored by the receiving device. The
controller ignores the parity bit of incoming data and sets the parity bit to odd,
even or none (mark parity) for outgoing data.
Stop Bit
The last character transmitted is the stop bit. The stop bit provides a single
bit period pause to allow the receiver to prepare to re-synchronize to the start
of new transmission (start bit of next byte). After the stop bit, the receiver
continuously looks for the occurrence of the next start bit.

Command Response Time

The controller can only receive or transmit data at any one time (half-duplex
operation). If bus activity, such as another command, occurs before the
controller has ended its transmission, garbled data will result. When sending
commands and data to the controller, timing restrictions are imposed when
sending another command afterwards. This allows enough time for the
controller to process the command and prepare for the next command. If the
timing requirements are not obeyed, lost transmissions may result.
Figure 35, Timing Diagram
At the start of the time interval t
string to the com port, thus initiating a transmission. During t
characters are transmitting and at the end of this period, the command
terminating character (*) is received by the controller. The time duration of t
is dependent on the number of characters and baud rate of the channel.
-62-
, the computer program prints or writes the
1
, the command
1
1