3803L Datasheet, PDF (98/119 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

3803 Group (Spec.L)
Notes on Serial Interface
1. Notes when selecting clock synchronous serial I/O
(1) Stop of transmission operation
As for serial I/Oi (i = 1, 3) that can be used as either a clock
synchronous or an asynchronous (UART) serial I/O, clear the
serial I/Oi enable bit and the transmit enable bit to “0” (serial
I/Oi and transmit disabled).
<Reason>
Since transmission is not stopped and the transmission circuit is
not initialized even if only the serial I/Oi enable bit is cleared to
“0” (serial I/Oi disabled), the internal transmission is running (in
this case, since pins TxDi, RxDi, SCLKi, and SRDYi function as
I/O ports, the transmission data is not output). When data is
written to the transmit buffer register in this state, data starts to
be shifted to the transmit shift register. When the serial I/Oi
enable bit is set to “1” at this time, the data during internally
shifting is output to the TxDi pin and an operation failure occurs.
(2) Stop of receive operation
As for serial I/Oi (i = 1, 3) that can be used as either a clock
synchronous or an asynchronous (UART) serial I/O, clear the
receive enable bit to “0” (receive disabled), or clear the serial
I/Oi enable bit to “0” (serial I/Oi disabled).
3. SRDYi (i = 1, 3) output of reception side
When signals are output from the SRDYi pin on the reception side
by using an external clock in the clock synchronous serial I/O
mode, set all of the receive enable bit, the SRDYi output enable
bit, and the transmit enable bit to “1” (transmit enabled).
4. Setting serial I/Oi (i = 1, 3) control register again
Set the serial I/Oi control register again after the transmission
and the reception circuits are reset by clearing both the transmit
enable bit and the receive enable bit to “0.”
Clear both the transmit enable bit (TE) and
the receive enable bit (RE) to “0”
Set the bits 0 to 3 and bit 6 of the serial I/Oi
control register
Set both the transmit enable bit (TE) and the
receive enable bit (RE), or one of them to “1”
Can be set with the
LDM instruction at
the same time
(3) Stop of transmit/receive operation
As for serial I/Oi (i = 1, 3) that can be used as either a clock
synchronous or an asynchronous (UART) serial I/O, clear both
the transmit enable bit and receive enable bit to “0” (transmit and
receive disabled).
(when data is transmitted and received in the clock synchronous
serial I/O mode, any one of data transmission and reception
cannot be stopped.)
<Reason>
In the clock synchronous serial I/O mode, the same clock is used
for transmission and reception. If any one of transmission and
reception is disabled, a bit error occurs because transmission and
reception cannot be synchronized.
In this mode, the clock circuit of the transmission circuit also
operates for data reception. Accordingly, the transmission circuit
does not stop by clearing only the transmit enable bit to “0”
(transmit disabled). Also, the transmission circuit is not
initialized by clearing the serial I/Oi enable bit to “0” (serial I/Oi
disabled) (refer to (1) in 1.).
2. Notes when selecting clock asynchronous serial I/O
(1) Stop of transmission operation
Clear the transmit enable bit to “0” (transmit disabled). The
transmission operation does not stop by clearing the serial I/Oi
enable bit (i = 1, 3) to “0”.
<Reason>
This is the same as (1) in 1.
(2) Stop of receive operation
Clear the receive enable bit to “0” (receive disabled).
(3) Stop of transmit/receive operation
Only transmission operation is stopped.
Clear the transmit enable bit to “0” (transmit disabled). The
transmission operation does not stop by clearing the serial I/Oi
enable bit (i = 1, 3) to “0”.
<Reason>
This is the same as (1) in 1.
Only receive operation is stopped.
Clear the receive enable bit to “0” (receive disabled).
Fig 97. Sequence of setting serial I/Oi (i = 1, 3) control
register again
5. Data transmission control with referring to transmit
shift register completion flag
After the transmit data is written to the transmit buffer register,
the transmit shift register completion flag changes from “1” to
“0” with a delay of 0.5 to 1.5 shift clocks. When data
transmission is controlled with referring to the flag after writing
the data to the transmit buffer register, note the delay.
6. Transmission control when external clock is selected
When an external clock is used as the synchronous clock for data
transmission, set the transmit enable bit to “1” at “H” of the
SCLKi (i = 1, 3) input level. Also, write the transmit data to the
transmit buffer register at “H” of the SCLKi input level.
7. Transmit interrupt request when transmit enable bit
is set
When using the transmit interrupt, take the following sequence.
(1) Set the serial I/Oi transmit interrupt enable bit (i = 1, 3) to
“0” (disabled).
(2) Set the tranasmit enable bit to “1”.
(3) Set the serial I/Oi transmit interrupt request bit (i = 1, 3) to
“0” after 1 or more instruction has executed.
(4) Set the serial I/Oi transmit interrupt enable bit (i = 1, 3) to
“1” (enabled).
<Reason>
When the transmission enable bit is set to “1”, the transmit buffer
empty flag and transmit shift register shift completion flag are
also set to “1”.
Therefore, regardless of selecting which timing for the
generating of transmit interrupts, the interrupt request is
generated and the transmit interrupt request bit is set at this point.
8. Writing to baud rate generator i (BRGi) (i = 1, 3)
Write data to the baud rate generator i (BRGi) (i = 1, 3) while the
transmission/reception operation is stopped.
Rev.1.01 Jan 25, 2008 Page 98 of 117
REJ03B0212-0101