CHAPTER 11 SERIAL INTERFACE UART0 (
µ
PD78F0102H AND 78F0103H ONLY)
Preliminary User’s Manual U16846EJ1V0UD
218
11.4.3 Dedicated baud rate generator
The dedicated baud rate generator consists of a source clock selector and a 5-bit programmable counter, and
generates a serial clock for transmission/reception of UART0.
Separate 5-bit counters are provided for transmission and reception.
(1) Configuration of baud rate generator
•
Base clock
The clock selected by bits 7 and 6 (TPS01 and TPS00) of baud rate generator control register 0 (BRGC0) is
supplied to each module when bit 7 (POWER0) of asynchronous serial interface operation mode register 0
(ASIM0) is 1. This clock is called the base clock and its frequency is called f
XCLK0
. The base clock is fixed
to low level when POWER0 = 0.
•
Transmission
counter
This counter stops, cleared to 0, when bit 7 (POWER0) or bit 6 (TXE0) of asynchronous serial interface
operation mode register 0 (ASIM0) is 0.
It starts counting when POWER0 = 1 and TXE0 = 1.
The counter is cleared to 0 when the first data transmitted is written to transmit shift register 0 (TXS0).
•
Reception
counter
This counter stops operation, cleared to 0, when bit 7 (POWER0) or bit 5 (RXE0) of asynchronous serial
interface operation mode register 0 (ASIM0) is 0.
It starts counting when the start bit has been detected.
The counter stops operation after one frame has been received, until the next start bit is detected.
Figure 11-11. Configuration of Baud Rate Generator
f
XCLK0
Selector
POWER0
5-bit counter
Match detector
Baud rate
BRGC0: MDL04 to MDL00
1/2
POWER0, TXE0 (or RXE0)
BRGC0: TPS01, TPS00
8-bit timer/
event counter
50 output
f
X
/2
5
f
X
/2
f
X
/2
3
Baud rate generator
Remark POWER0: Bit 7 of asynchronous serial interface operation mode register 0 (ASIM0)
TXE0:
Bit 6 of ASIM0
RXE0:
Bit 5 of ASIM0
BRGC0:
Baud rate generator control register 0