OXCB950
OXFORD SEMICONDUCTOR LTD.
7.6 Interrupts & Sleep Mode
The serial channel interrupts are asserted on the PCI
INTA# pin. The interrupts can be enabled or disabled using
the GIS register interrupt mask (see section 6.4.4) and the
IER register. Unlike generic 16C550 devices, the interrupt
can not be disabled using the implementation-specific
MCR[3].
In 9-bit data mode, The receiver can detect up to four
special characters programmed in the Special Character
Registers (see map on page 31). When IER[5] is set, a
level 5 interrupt is asserted when the receiver character
matches one of the values programmed.
650/950 modes (non-9-bit data framing):
logic 0 ⇒ Disable the special character receive interrupt.
logic 1 ⇒ Enable the special character receive interrupt.
7.6.1 Interrupt Enable Register ‘IER’
Serial channel interrupts are enabled using the Interrupt
Enable Register (‘IER’).
In 16C650 compatible mode when the device is in
Enhanced mode (EFR[4]=1), this bit enables the detection
of special characters. It enables both the detection of
XOFF characters (when in-band flow control is enabled via
EFR[3:0]) and the detection of the XOFF2 special
character (when enabled via EFR[5]).
IER[0]: Receiver data available interrupt mask
logic 0 ⇒ Disable the receiver ready interrupt.
logic 1 ⇒ Enable the receiver ready interrupt.
IER[1]: Transmitter empty interrupt mask
logic 0 ⇒ Disable the transmitter empty interrupt.
logic 1 ⇒ Enable the transmitter empty interrupt.
750 mode (non-9-bit data framing):
logic 0 ⇒ Disable alternate sleep mode.
logic 1 ⇒ Enable alternate sleep mode whereby the
internal clock of the channel is switched off.
IER[2]: Receiver status interrupt
Normal mode:
logic 0 ⇒ Disable the receiver status interrupt.
logic 1 ⇒ Enable the receiver status interrupt.
9-bit data mode:
In 16C750 compatible mode (i.e. non-Enhanced mode),
this bit is used an alternate sleep mode and has the same
effect as IER[4].
logic 0 ⇒ Disable receiver status and address bit
interrupt.
IER[6]: RTS interrupt mask
logic 1 ⇒ Enable receiver status and address bit
interrupt.
logic 0 ⇒ Disable the RTS interrupt.
logic 1 ⇒ Enable the RTS interrupt.
In 9-bit mode (i.e. when NMR[0] is set), reception of a
This enable is only operative in Enhanced mode
(EFR[4]=1). In non-Enhanced mode, RTS interrupt is
permanently enabled
th
character with the address-bit (i.e. 9 bit) set can generate
a level 1 interrupt if IER[2] is set.
IER[3]: Modem status interrupt mask
IER[7]: CTS interrupt mask
logic 0 ⇒ Disable the modem status interrupt.
logic 1 ⇒ Enable the modem status interrupt.
logic 0 ⇒ Disable the CTS interrupt.
logic 1 ⇒ Enable the CTS interrupt.
IER[4]: Sleep mode
This enable is only operative in Enhanced mode
(EFR[4]=1). In non-Enhanced mode, CTS interrupt is
permanently enabled.
logic 0 ⇒ Disable sleep mode.
logic 1 ⇒ Enable sleep mode whereby the internal clock
of the channel is switched off.
Sleep mode is described in section 7.6.4.
IER[5]: Special character interrupt mask or alternate
sleep mode
9-bit data framing mode:
logic 0 ⇒ Disable the received special character interrupt.
logic 1 ⇒ Enable the received special character interrupt.
DS-0033 Sep 05
External-Free Release
Page 38
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