sc28l198 NXP Semiconductors, sc28l198 Datasheet - Page 17

• Manufacturer Part Number: sc28l198
• Description: Octal Uart For 3.3v And 5v Supply Voltage
• Manufacturer: NXP Semiconductors

transmitted depending on the timing with the transmit state machine.
Note: In no case will an Xon/Xoff character transmission be aborted.
Philips Semiconductors
activity of the Xon/Xoff logic is initiated by commands to the CRx
command forces the transmitter to disable exactly as though an Xoff
character had been received by the RxFIFO. The transmitter will
remain disabled until the chip is reset or the CR(7:3) = 10110 (Xoff
resume) command is given. In particular, reception of an Xon or
disabling or re–enabling the transmitter will NOT cause resumption
of transmission. Redundant CRTXon/off commands, i.e. CRTXon
CRTXon, are harmless, although they waste time. A CRTXon may
be used to cancel a CRTXoff (and vice versa), but both may be
The kill CRTX command can be used to cleanly terminate any
CRTX commands pending with the minimum impact on the
transmitter.
Once the character is loaded into the TX Shift Register, transmission
continues until completion or a chip reset is encountered.
The kill CRTX command has no effect in either of the Auto modes.
Mode control
Xon/Xoff mode control is accomplished via the MR0. Bits 3 and 2
reset to zero resulting in all Xon/Xoff processing being disabled. If
MR0[2] is set, the transmitter may be gated by Xon/Xoff characters
received. If MR0[3] is set, the transmitter will transmit Xon and Xoff
when triggered by attainment of fixed fill levels in the channel
RxFIFO. The MR0[7] bit also has an Xon/Xoff function control. If
this bit is set, a received Xon or Xoff character is not pushed into the
RxFIFO. If cleared, the power–on and reset default, the received
2006 Aug 10
Octal UART for 3.3 V and 5 V supply voltage
17
Xon or Xoff character is pushed onto the RxFIFO for examination by
the host CPU. The MR0(7) function operates regardless of the
value in MR0(3:2)
Xon/Xoff Interrupts
The Xon/Xoff logic generates interrupts only in response to
recognizing either of the characters in the XonCR or XoffCR (Xon or
Xoff Character Registers). The transmitter activity initiated by the
Xon/Xoff logic or any CR command does not generate an interrupt.
The character comparators operate regardless of the value in
MR0(3:2). Hence the comparators may be used as general purpose
character detectors by setting MR0(3:2)=’00’ and enabling the
Xon/Xoff interrupt in the IMR.
The Octal UART can present the Xon/Xoff recognition event to the
interrupt arbiter for IRQN generation. The IRQN generation may be
masked by setting bit 4 of the Interrupt Mask Register, IMR. The bid
level of an Xon/Xoff recognition event is controlled by the Bidding
Control Register X, BCRX, of the channel. The interrupt status can
be examined in ISR[4]. If cleared, no Xon/Xoff recognition event is
interrupting. If set, an Xon or Xoff recognition event has been
detected. The X Interrupt Status Register, XISR, can be read for
details of the interrupt and to examine other, non–interrupting, status
of the Xon/Xoff logic. Refer to the XISR in the Register
Descriptions.
The character recognition function and the associated interrupt
generation is disabled on hardware or software reset.
SC28L198
Product data sheet