p87lpc778 NXP Semiconductors, p87lpc778 Datasheet - Page 50

• Manufacturer Part Number: p87lpc778
• Description: Cmos Single-chip 8-bit 80c51 Microcontroller 128-byte Data Ram, 8 Kb Otp
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 12378
Product data
Fig 22. Timer/counter 0 Mode 3 (two 8-bit counters).
or Osc/12
INT0 pin
T0 pin
Osc/6
Gate
TR0
8.14.5 Timer overflow toggle output
8.15 UART
Timers 0 and 1 can be configured to automatically toggle a port output whenever a
timer overflow occurs. The same device pins that are used for the T0 and T1 count
inputs are also used for the timer toggle outputs. This function is enabled by control
bits ENT0 and ENT1 in the P2M1 register, and apply to Timer0 and Timer1
respectively. The port outputs will be a logic 1 prior to the first timer overflow when
this mode is turned on.
The P87LPC778 includes an enhanced 80C51 UART. The baud rate source for the
UART is Timer1 for modes 1 and 3, while the rate is fixed in modes 0 and 2. Because
CPU clocking is different on the P87LPC778 than on the standard 80C51, baud rate
calculation is somewhat different. Enhancements over the standard 80C51 UART
include Framing Error detection and automatic address recognition.
The serial port is full duplex, meaning it can transmit and receive simultaneously. It is
also receive-buffered, meaning it can commence reception of a second byte before a
previously received byte has been read from the SBUF register. However, if the first
byte still hasn’t been read by the time reception of the second byte is complete, the
first byte will be lost. The serial port receive and transmit registers are both accessed
through Special Function Register SBUF. Writing to SBUF loads the transmit register,
and reading SBUF accesses a physically separate receive register.
The serial port can be operated in 4 modes.
or Osc/12
Osc/6
TR1
C/T = 0
C/T = 1
Rev. 01 — 31 March 2004
control
control
(8-bits)
(8-bits)
TH0
TL0
overflow
overflow
CMOS single-chip 8-bit microcontroller
toggle
toggle
TF1
TF0
T1OE
T0OE
002aaa640
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
interrupt
interrupt
P87LPC778
T1 pin
T0 pin
50 of 79