41CL User Manual
© 2019, Systemyde International Corporation
37
All of the serial data transfer functions contain a time-out feature to prevent locking up
the machine in the case of an unavailable serial port. This time-out period is dependent on
the Turbo mode, as shown in the table below:
Speed
Serial time-out period
1x
~15 seconds
2x
~12 seconds
all others
~7 seconds
In the absence of a valid RS-232 level on the serial receive input the RS-232 transceiver
automatically powers down. But whenever there is a valid RS-232 level on the receive
input the transceiver will be powered. This is a significant addition to the current drain on
the batteries, so the serial port should only be connected to a PC or other RS-232 equip-
ment when actually using the serial port.
The calculator should always be turned off while connecting or disconnecting the
serial port.
The recommended way to connect the serial port is to first insert the 2.5mm
plug into the calculator and then connect the other end to an active serial connection.
While the serial driver in the calculator is powering up the internal power supply may
droop low enough to trigger the power-on-reset, which automatically disables the MMU.
This droop is not sufficient to corrupt RAM contents, so the MMU programming will still
be valid. So, after turning on the calculator with the serial port connected for the first
time, it is advisable to make sure that the MMU is enabled before attempting to use the
serial functions.
The tension holding a 2.5mm plug in the serial connector jack is higher than the tension
holding the blank port cover in the calculator body. This means that trying to pull out the
plug will tend to pull the blank port cover out of the calculator, potentially damaging the
internal connections to the serial connector jack.
Always remember to hold the blank
port cover in place when attempting to remove the serial port plug from the calcula-
tor.
SERINI
Executing
SERINI
(
Initialize Serial Port
) initializes the serial port and sets the baud rate
to 1200. Both the transmit and receive buffers are emptied and the receiver and
transmitter are both set to the idle state. This command has no effect on the RS-232
driver.
