Dedicated Baud Rate Generator - NEC 78K0 User Manual

15.4.3 Dedicated baud rate generator

The dedicated baud rate generator consists of a source clock selector and an 8-bit programmable counter, and
generates a serial clock for transmission/reception of UART6.
Separate 8-bit counters are provided for transmission and reception.
(1) Configuration of baud rate generator
• Base clock
The clock selected by bits 3 to 0 (TPS63 to TPS60) of clock selection register 6 (CKSR6) is supplied to
each module when bit 7 (POWER6) of asynchronous serial interface operation mode register 6 (ASIM6) is
1. This clock is called the base clock and its frequency is called f
when POWER6 = 0.
• Transmission counter
This counter stops operation, cleared to 0, when bit 7 (POWER6) or bit 6 (TXE6) of asynchronous serial
interface operation mode register 6 (ASIM6) is 0.
It starts counting when POWER6 = 1 and TXE6 = 1.
The counter is cleared to 0 when the first data transmitted is written to transmit buffer register 6 (TXB6).
If data are continuously transmitted, the counter is cleared to 0 again when one frame of data has been
completely transmitted. If there is no data to be transmitted next, the counter is not cleared to 0 and continues
counting until POWER6 or TXE6 is cleared to 0.
• Reception counter
This counter stops operation, cleared to 0, when bit 7 (POWER6) or bit 5 (RXE6) of asynchronous serial
interface operation mode register 6 (ASIM6) 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.
CHAPTER 15 SERIAL INTERFACE UART6
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User's Manual U15947EJ2V0UD
. The base clock is fixed to low level
XCLK6
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