OXMPCI952 Datasheet, PDF (70/108 Pages) Oxford Semiconductor – Integrated High Performance Dual UARTs, 8-bit Local Bus/Parallel Port. 3.3v PCI/miniPCI interface.

OXFORD SEMICONDUCTOR LTD.
6.11.14 Clock Alteration Register ‘CKA’
The CKA register is located at offset 0x13 of the ICR. This
register adds additional clock control mainly for
isochronous and embedded applications. The register is
effectively an enhancement to the CKS register.
This register is cleared to 0x00 after a hardware reset to
maintain compatibility with 16C550, but is unaffected by
software reset. This allows the user to select a clock mode
and then reset the channel to work-around any timing
glitches.
CKA[0]: Invert internal RX Clock
This allows the sense of the receiver clock to be inverted.
The main use for this would be to invert an isochronous
input clock so the falling edge were used for sampling
rather than the rising edge.
OXmPCI952
CKA[1]: Invert internal TX clock
This allows the sense of the transmitter clock to be
inverted. The main use for this would be to invert an
isochronous input clock so the rising edge were used for
data output rather than the falling edge.
CKA[2]: Invert DTR
This allows the DTR output signal to be inverted, which is
most likely to be useful when DTR is selected as being the
transmitter clock for isochronous applications input clock so
the falling edge were used for sampling rather than the
rising edge.
DS-0020 Jun 05
Page 70