OX16PCI954_05 Datasheet, PDF (50/73 Pages) Oxford Semiconductor – Integrated Quad UART and PCI interface

OXFORD SEMICONDUCTOR LTD.
OX16PCI954
7.11.8 Clock Select Register ‘CKS’
The CKS register is located at offset 0x03 of the ICR
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
source and then reset the channel to work-around any
timing glitches.
CKS[1:0]: Receiver Clock Source Selector
logic [x0] ⇒ The output of baud rate generator (internal
BDOUT#) is selected for the receiver clock.
logic [01] ⇒ The DSR# pin is selected for the receiver
clock.
logic [11] ⇒ The transmitter clock is selected for the
receiver. This allows RI# to be used for both
transmitter and receiver.
CKS[2]: Reserved
CKS[3]: Receiver 1x clock mode selector
logic 0 ⇒ The receiver is in Nx clock mode as defined in
the TCR register. After a hardware reset the
receiver operates in 16x clock mode, i.e.
16C550 compatibility.
logic 1 ⇒ The receiver is in isochronous 1x clock mode.
CKS[5:4]: Transmitter 1x clock or baud rate generator
output (BDOUT) on DTR# pin
logic [00] ⇒ The function of the DTR# pin is defined by
the setting of ACR[4:3].
logic [01] ⇒ The transmitter 1x clock (bit rate clock) is
asserted on the DTR# pin and the setting of
ACR[4:3] is ignored.
logic [10] ⇒ The output of baud rate generator (Nx clock)
is asserted on the DTR# pin and the setting
of ACR[4:3] is ignored.
logic [11] ⇒ Reserved.
CKS[6]: Transmitter clock source selector
logic 0 ⇒ The transmitter clock source is the output of the
baud rate generator (550 compatibility).
logic 1 ⇒ The transmitter uses an external clock applied
to the RI# pin.
CKS[7]: Transmitter 1x clock mode selector
logic 0 ⇒ The transmitter is in Nx clock mode as defined
in the TCR register. After a hardware reset the
transmitter operates in 16x clock mode, i.e.
16C550 compatibility.
logic 1 ⇒ The transmitter is in isochronous 1x clock
mode.
7.11.9 Nine-bit Mode Register ‘NMR’
The NMR register is located at offset 0x0D of the ICR
The UART offers 9-bit data framing for industrial multi-drop
applications. The 9-bit mode is enabled by setting bit 0 of
the Nine-bit Mode Register (NMR). In 9-bit mode the data
length setting in LCR[1:0] is ignored. Furthermore as parity
is permanently disabled, the setting of LCR[5:3] is also
ignored.
The receiver stores the 9th bit of the received data in
LSR[2] (where parity error is stored in normal mode). Note
that the UART provides a 128-deep FIFO for LSR[3:0].
The transmitter FIFO is 9 bits wide and 128 deep. The user
should write the 9th (MSB) data bit in SPR[0] first and then
write the other 8 bits to THR.
As parity mode is disabled, LSR[7] is set whenever there is
an overrun, framing error or received break condition. It is
unaffected by the contents of LSR[2] (Now the received 9th
data bit).
In 9-bit mode, in-band flow control is disabled regardless of
the setting of EFR[3:0] and the XON1/XON2/XOFF1 and
XOFF2 registers are used for special character detection.
Interrupts in 9-Bit Mode:
While IER[2] is set, upon receiving a character with status
error, a level 1 interrupt is asserted when the character and
the associated status are transferred to the FIFO.
The UART can assert an optional interrupt if a received
character has its 9^th bit set. As multi-drop systems often
use the 9^th bit as an address bit, the receiver is able to
generate an interrupt upon receiving an address character.
This feature is enabled by setting NMR[2]. This will result
in a level 1 interrupt being asserted when the address
character is transferred to the receiver FIFO.
In this case, as long as there are no errors pending, i.e.
LSR[1], LSR[3], and LSR[4] are clear, '0' can be read back
from LSR[7] and LSR[1], thus differentiating between an
‘address’ interrupt and receiver error or overrun interrupt in
9-bit mode. Note however that should an overrun or error
interrupt actually occur, an address character may also
reside in the FIFO. In this case, the software driver should
examine the contents of the receiver FIFO as well as
process the error.
DS-0029 Jul 05
External—Free Release
Page 50