p89lpc9401 NXP Semiconductors, p89lpc9401 Datasheet - Page 28

• Manufacturer Part Number: p89lpc9401
• Description: 8-bit Microcontroller With Accelerated Two-clock 80c51 Core 8 Kb 3 V Byte-erasable Flash With 32 Segment X 4 Lcd Driver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
P89LPC9401_1
Preliminary data sheet
7.19.10 The 9
7.19.9 Transmit interrupts with double buffering enabled (modes 1, 2 and 3)
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)
8-bit two-clock 80C51 microcontroller with 32 segment
Rev. 01 — 5 September 2005
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
P89LPC9401
4 LCD driver
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