Serial Port Downloads to 41CL

[Monte Dalrymple]

It IS possible to check the CL serial port hardware with a V4 board, but it requires some care. You just need to create a loopback connection. At the DB9 end of the serial cable somehow connect the RX signal to the TX signal. A piece of wire might work, but you'll get a better connection if you have a gender-changer so that you can connect to pins directly. Set the baud rate (any will do) and enable the serial port (this is the step that requires a V4 board) using the SERON function in YFNX. Then if you YPOKE a byte directly to the transmit buffer the byte will be transmitted. Then you just need to YPEEK the serial port status register to verify that the tx buffer is empty and the rx buffer is full. Then YPEEK the receive buffer to check that the byte arrived. You'll need to look at the NEWT manual to find the addresses of the serial port registers, and the YPEEK/YPOKE description in the manual to see the proper formatting for a peripheral address. This is how I first tested the serial port, although I had to use an external power supply to transiently force a valid RS232 level on the wire to enable the serial port.