M3850 Datasheet, PDF (84/88 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

3850 Group (Spec.A)
PRELIMINARY
Notice: This is not a final specification.
Some parametric limits are subject to change.
2. Notes when selecting clock asynchronous serial I/O (Serial I/O1)
(1) Stop of transmission operation
Clear the transmit enable bit to “0” (transmit disabled).
<Reason>
Since transmission is not stopped and the transmission circuit is
not initialized even if only the serial I/O1 enable bit is cleared to “0”
(Serial I/O1 disabled), the internal transmission is running (in this
case, since pins TxD, RxD, SCLK1, and SRDY1 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/O1 enable bit is set to
“1” at this time, the data during internally shifting is output to the
TxD pin and an operation failure occurs.
(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).
<Reason>
Since transmission is not stopped and the transmission circuit is
not initialized even if only the serial I/O1 enable bit is cleared to “0”
(Serial I/O1 disabled), the internal transmission is running (in this
case, since pins TxD, RxD, SCLK1, and SRDY1 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/O1 enable bit is set to
“1” at this time, the data during internally shifting is output to the
TxD pin and an operation failure occurs.
Only receive operation is stopped.
Clear the receive enable bit to “0” (receive disabled).
3. Setting serial I/O1 control register again (Serial I/O1)
Set the serial I/O1 control register again after the transmission and
the reception circuits are reset by clearing both the transmit en-
able 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/O1
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
Fig. 6 Sequence of setting serial I/O1 control register again
4. Data transmission control with referring to transmit shift register
completion flag (Serial I/O1)
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.
5. Transmit interrupt request when transmit enable bit is set (Serial
I/O1)
When the transmit interrupt is used, set the transmit interrupt en-
able bit to transmit enabled as shown in the following sequence.
(1) Set the interrupt enable bit to “0” (disabled) with CLB instruction.
(2) Prepare serial I/O for transmission/reception.
(3) Set the interrupt request bit to “0” with CLB instruction after 1
or more instruction has been executed.
(4) Set the interrupt enable bit to “1” (enabled).
<Reason>
When the transmission enable bit is set to “1”, the transmit buffer
empty flag and transmit shift register completion flag are set to “1”.
The interrupt request is generated and the transmission interrupt
request bit is set regardless of which of the two timings listed be-
low is selected as the timing for the transmission interrupt to be
generated.
• Transmit buffer empty flag is set to “1”
• Transmit shift register completion flag is set to “1”
6. Transmission control when external clock is selected (Serial I/
O1 clock synchronous mode)
When an external clock is used as the synchronous clock for data
transmission, set the transmit enable bit to “1” at “H” of the SCLK1
input level. Also, write the transmit data to the transmit buffer reg-
ister (serial I/O shift register) at “H” of the SCLK1 input level.
7. Transmit data writing (Serial I/O2)
In the clock synchronous serial I/O, when selecting an external
clock as synchronous clock, write the transmit data to the serial
I/O2 register (serial I/O shift register) at “H” of the transfer clock in-
put level.
Notes on PWM
The PWM starts after the PWM enable bit is set to enable and “L”
level is output from the PWM pin.
The length of this “L“ level output is as follows:
n+1
2 • f(XIN)
n+1
f(XIN)
sec. (Count source selection bit = “0”,
where n is the value set in the prescaler)
sec. (Count source selection bit = “1”,
where n is the value set in the prescaler)
Rev.2.10 2005.11.14 page 84 of 86
REJ03B0093-0210