P89LPC925 PHILIPS [NXP Semiconductors], P89LPC925 Datasheet - Page 30

• Manufacturer Part Number: P89LPC925
• Description: 8-bit microcontrollers with accelerated two-clock 80C51 core 4 kB/8 kB 3 V low-power Flash with 8-bit A/D converter
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
9397 750 14471
Product data
8.19.10 The 9
8.19.6 Framing error
8.19.7 Break detect
8.19.8 Double buffering
8.19.9 Transmit interrupts with double buffering enabled (Modes 1, 2 and 3)
Framing error is reported in the status register (SSTAT). In addition, if SMOD0
(PCON.6) is ‘1’, framing errors can be made available in SCON.7 respectively. If
SMOD0 is ‘0’, SCON.7 is SM0. It is recommended that SM0 and SM1 (SCON.7:6)
are set up when SMOD0 is ‘0’.
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. 03 — 15 December 2004
8-bit microcontrollers with accelerated two-clock 80C51 core
P89LPC924/925
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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