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4UART-USB

Overview

The ECB 4UART-USB board provides four 8250/16C550 similar serial interfaces using the TL16C754B or SC16C754B PLCC chip, which is clocked from 48mhz down to 1.8432mhz. Two of the serial outputs are dedicated to USB ports through a separate FT232RL adapter, and the remaining two outputs may be RS-232 terminal connections, or individually selected as USB connections. Bit rates up to 3mbps are possible, with the proviso that all interfaces use the same clock. With high clock rates, even bit rates down to 110bps are still achievable with large divisors.

Testing indicates that the TL16C754B chips are very sensitive to the relative timing of CSx# and IOW#. CSx# must fall 10ns before IOW#. One way to achieve this is to fit 74ALS139 or 74AHCT139 in place of 74LS139, and use 74LS on the rest of the board (with the exception of the 74F00). SC16C754B does not appear to suffer from this sensitivity.

boards/ecb/4uart-usb/start.1531557814.txt.gz · Last modified: 2018/07/14 04:43 by b1ackmai1er
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