OXCB950
OXFORD SEMICONDUCTOR LTD.
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The UART is not in loopback mode (MCR[4]=0).
Changes on modem input lines have been
acknowledged (i.e. MSR[3:0]=0000).
Level 6:
CTS or RTS changed interrupt (ISR[5:0]=’100000’):
This interrupt is set whenever any of the CTS# or RTS#
pins changes state from low to high. It is cleared on an ISR
read of a level 6 interrupt.
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No interrupts are pending.
A read of IER[4] (or IER[5] if a 1 was written to that bit
instead) shows whether the power-down request was
successful. The UART will retain its programmed state
whilst in power-down mode.
7.6.4 Sleep Mode
For a channel to go into sleep mode, all of the following
conditions must be met:
The channel will automatically exit power-down mode when
any of the conditions 1 to 7 becomes false. It may be
woken manually by clearing IER[4] (or IER[5] if the
alternate sleep mode is enabled).
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Sleep mode enabled (IER[4]=1 in 650/950 modes, or
IER[5]=1 in 750 mode):
The transmitter is idle, i.e. the transmitter shift register
and FIFO are both empty.
Sleep mode operation is not available in IrDA mode.
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SIN is high.
The receiver is idle.
The receiver FIFO is empty (LSR[0]=0).
7.7 Modem Interface
MCR[4]: Loopback mode
7.7.1 Modem Control Register ‘MCR’
MCR[0]: DTR
logic 0 ⇒ Normal operating mode.
logic 1 ⇒ Enable local loop-back mode (diagnostics).
logic 0 ⇒ Force DTR# output to inactive (high).
logic 1 ⇒ Force DTR# output to active (low).
In local loop-back mode, the transmitter output (SOUT) and
the four modem outputs (DTR#, RTS#, OUT1# and
OUT2#) are set in-active (high), and the receiver inputs
SIN, CTS#, DSR#, DCD#, and RI# are all disabled.
Internally the transmitter output is connected to the receiver
input and DTR#, RTS#, OUT1# and OUT2# are connected
to modem status inputs DSR#, CTS#, RI# and DCD#
respectively.
Note that DTR# can be used for automatic out-of-band flow
control when enabled using ACR[4:3] (see section 7.11.3).
MCR[1]: RTS
logic 0 ⇒ Force RTS# output to inactive (high).
logic 1 ⇒ Force RTS# output to active (low).
Note that RTS# can be used for automatic out-of-band flow
control when enabled using EFR[6] (see section 7.9.4).
In this mode, the receiver and transmitter interrupts are
fully operational. The modem control interrupts are also
operational, but the interrupt sources are now the lower
four bits of the Modem Control Register instead of the four
modem status inputs. The interrupts are still controlled by
the IER.
MCR[2]: OUT1
logic 0 ⇒ Force OUT1# output low when loopback mode
is disabled.
logic 1 ⇒ Force OUT1# output high.
MCR[5]: Enable XON-Any in Enhanced mode or enable
out-of-band flow control in non-Enhanced mode
MCR[3]: OUT2/External interrupt enable
logic 0 ⇒ Force OUT2# output low when loopback mode
is disabled. If INT_SEL# is low the external
interrupt is in high-impedance state when
MCR[3] is cleared. If INT_SEL# is high MCR[3]
does not affect the interrupt.
650/950 (enhanced) modes:
logic 0 ⇒ XON-Any is disabled.
logic 1 ⇒ XON-Any is enabled.
In enhanced mode (EFR[4]=1), this bit enables the Xon-
Any operation. When Xon-Any is enabled, any received
data will be accepted as a valid XON (see in-band flow
control, section 7.9.3).
logic 1 ⇒ Force OUT2# output high. If INT_SEL# is low
the external interrupt is enabled and operating
in normal active (forcing) mode when MCR[3] is
high. If INT_SEL# is high MCR[3] does not
affect the interrupt.
DS-0033 Sep 05
External-Free Release
Page 40
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