P89LPC930_931 NXP Semiconductors, P89LPC930_931 Datasheet - Page 29

• Manufacturer Part Number: P89LPC930_931
• Description: The P89LPC930/931 are single-chip microcontrollers designed for applicationsdemanding high-integration, low cost solutions over a wide range of performancerequirements
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 14472
Product data
8.17.10 The 9
8.17.7 Break detect
8.17.8 Double buffering
8.17.9 Transmit interrupts with double buffering enabled (Modes 1, 2 and 3)
Break detect is reported in the status register (SSTAT). A break is detected when
11 consecutive bits are sensed LOW. The break detect can be used to reset the
device and force the device into ISP mode.
The UART has a transmit double buffer that allows buffering of the next character to
be written to SBUF while the first character is being transmitted. Double buffering
allows transmission of a string of characters with only one stop bit between any two
characters, as long as the next character is written between the start bit and the stop
bit of the previous character.
Double buffering can be disabled. If disabled (DBMOD, i.e., SSTAT.7 = ‘0’), the UART
is compatible with the conventional 80C51 UART. If enabled, the UART allows writing
to SnBUF while the previous data is being shifted out. Double buffering is only
allowed in Modes 1, 2 and 3. When operated in Mode 0, double buffering must be
disabled (DBMOD = ‘0’).
Unlike the conventional UART, in double buffering mode, the Tx interrupt is generated
when the double buffer is ready to receive new data.
If double buffering is disabled TB8 can be written before or after SBUF is written, as
long as TB8 is updated some time before that bit is shifted out. TB8 must not be
changed until the bit is shifted out, as indicated by the Tx interrupt.
If double buffering is enabled, TB8 must be updated before SBUF is written, as TB8
will be double-buffered together with SBUF data.
th
bit (bit 8) in double buffering (Modes 1, 2 and 3)
Rev. 05 — 15 December 2004
8-bit microcontrollers with two-clock 80C51 core
P89LPC930/931
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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