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Programming | 7
JCM-501-E00 User Manual
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Number
Section
Features
4
Receive register
Read access to this register reads the re-
ceived characters in the receive buffer
(3).
5
Interface driver
Converts internal signal levels into inter-
face signals.
6
Transmitter
Performs parallel/serial conversion
7
Sending buffer
Buffer for characters to be sent
8
Transmit register
Write access to this register causes the
characters to be entered into the transmit
buffer (7) and to be sent by the transmit-
ter (6).
9
Status and control register Query of filling levels and error states of
buffers; setting of transmission parame-
ters
Tab. 19:
Elements of the serial interface
Receiving a charac-
ter
Receiving a character is done in 4 steps:
Step
Description
1
The interface driver converts signals "on the line" into internal signal
levels and forwards them to the receiver.
2
The receiver performs serial/parallel conversion of this character and
checks the set communication parameters.
3
The receiver enters the character into the receive buffer if there is any
place left. Otherwise, the character is discarded and buffer overflow is
signaled.
4
Via receive register the character can be read out of the receive buffer.
Sending a charac-
ter
A character is sent in 4 steps:
Step
Description
1
Via transmit register the character is entered into the transmit buffer if
there is any place left. Otherwise the character is discarded.
2
Once the transmitter has sent a character, it reads the next character
from the transmit buffer.
3
The transmitter performs parallel/serial conversion and sends this char-
acter to the interface driver using the set communication parameters.
4
The interface driver converts internal signal levels into the various inter-
face standards
Error detection
When receiving characters, the following errors are detected by the controller and
displayed in the register
Error state
:
Errors
Description
Effect
Framing error
The format of the received
character does not match the
set parameters.
The erroneous character(s) is
(are) stored in the receive buf-
fer and error bit
Framing error
is set. The error counter is in-
cremented.
