P89LPC925 PHILIPS [NXP Semiconductors], P89LPC925 Datasheet - Page 29

• 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
8.19.1 Mode 0
8.19.2 Mode 1
8.19.3 Mode 2
8.19.4 Mode 3
8.19.5 Baud rate generator and selection
Serial data enters and exits through RxD. TxD outputs the shift clock. 8 bits are
transmitted or received, LSB first. The baud rate is fixed at
frequency.
10 bits are transmitted (through TxD) or received (through RxD): a start bit
(logical ‘0’), 8 data bits (LSB first), and a stop bit (logical ‘1’). When data is received,
the stop bit is stored in RB8 in Special Function Register SCON. The baud rate is
variable and is determined by the Timer 1 overflow rate or the Baud Rate Generator
(described in
11 bits are transmitted (through TxD) or received (through RxD): start bit (logical ‘0’),
8 data bits (LSB first), a programmable 9
data is transmitted, the 9
‘1’. Or, for example, the parity bit (P, in the PSW) could be moved into TB8. When
data is received, the 9
while the stop bit is not saved. The baud rate is programmable to either
the CPU clock frequency, as determined by the SMOD1 bit in PCON.
11 bits are transmitted (through TxD) or received (through RxD): a start bit
(logical ‘0’), 8 data bits (LSB first), a programmable 9
(logical ‘1’). In fact, Mode 3 is the same as Mode 2 in all respects except baud rate.
The baud rate in Mode 3 is variable and is determined by the Timer 1 overflow rate or
the Baud Rate Generator (described in
selection”).
The P89LPC924/925 enhanced UART has an independent Baud Rate Generator.
The baud rate is determined by a baud-rate preprogrammed into the BRGR1 and
BRGR0 SFRs which together form a 16-bit baud rate divisor value that works in a
similar manner as Timer 1 but is much more accurate. If the baud rate generator is
used, Timer 1 can be used for other timing functions.
The UART can use either Timer 1 or the baud rate generator output (see
Note that Timer T1 is further divided by 2 if the SMOD1 bit (PCON.7) is set. The
independent Baud Rate Generator uses OSCCLK.
Fig 7. Baud rate sources for UART (Modes 1, 3).
Baud Rate Generator
Timer 1 Overflow
(CCLK-based)
(PCLK-based)
Section 8.19.5 “Baud rate generator and
Rev. 03 — 15 December 2004
8-bit microcontrollers with accelerated two-clock 80C51 core
th
data bit goes into RB8 in Special Function Register SCON,
th
data bit (TB8 in SCON) can be assigned the value of ‘0’ or
¸
2
SMOD1 = 1
SMOD1 = 0
Section 8.19.5 “Baud rate generator and
th
data bit, and a stop bit (logical ‘1’). When
SBRGS = 0
SBRGS = 1
P89LPC924/925
th
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
selection”).
data bit, and a stop bit
1
16
Baud Rate Modes 1 and 3
of the CPU clock
1
002aaa419
16
Figure
or
1
29 of 49
32
7).
of