M37542F8FP Renesas Electronics America, M37542F8FP Datasheet - Page 117

• Manufacturer Part Number: M37542F8FP
• Description: IC 740 MCU FLASH 32K 36SSOP
• Manufacturer: Renesas Electronics America
• Series: 740/38000r

Specifications of M37542F8FP

• Core Processor: 740
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: SIO, UART/USART
• Peripherals: POR, WDT
• Number Of I /o: 29
• Program Memory Size: 32KB (32K x 8)
• Program Memory Type: FLASH
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.2 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -20°C ~ 85°C
• Package / Case: 36-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -

7542 Group
Rev.3.03
REJ03B0006-0303
Notes on A/D conversion
1. Analog input pin
Make the signal source impedance for analog input low, or equip
an analog input pin with an external capacitor of 0.01µF to 1µF.
Further, be sure to verify the operation of application products on
the user side.
<Reason>
An analog input pin includes the capacitor for analog voltage com-
parison. Accordingly, when signals from signal source with high
impedance are input to an analog input pin, charge and discharge
noise generates. This may cause the A/D conversion/comparison
precision to be worse.
2. Clock frequency during A/D conversion
The comparator consists of a capacity coupling, and a charge of
the capacity will be lost if the clock frequency is too low. This may
cause the A/D conversion precision to be worse. Accordingly, set
f(X
during A/D conversion.
3. A/D conversion clock selection
Select f(X
version clock selection bit (bit 3 of A/D control register (address
34
The f(X
ceramic oscillation or on-chip oscillator is used.
4. Analog input pin selection
P2
age version.
5. Read A/D conversion register
• 8-bit read
Read only the A/D conversion low-order register (address 35
•10-bit read
Read the A/D conversion high-ordrer register (address 36
and then, read the A/D conversion low-order register (address
35
In this case, the high-order 6 bits of address 36
when read.
16
16
6
IN
/AN
)) when RC oscillation is used.
).
) in order that the A/D conversion clock is 250 kHz or over
IN
6
) can be also used as an A/D conversion clock only when
and P2
IN
)/2 as an A/D conversion clock by setting the A/D con-
Jul 11, 2008
7
/AN
7
can be used only for PRSP0036GA-A pack-
Page 115 of 117
16
returns “0”
16
) first,
16
).
6. A/D conversion accuracy
As for AD translation accuracy, on the following operating condi-
tions, accuracy may become low.
(1) Since the analog circuit inside a microcomputer becomes sen-
(2) When V
Notes on Watchdog Timer
1. The watchdog timer is operating during the wait mode. Write
2. The watchdog timer stops during the stop mode. However, the
3. The STP instruction function selection bit (bit 6 of watchdog
4. A count source of watchdog timer is affected by the clock divi-
Notes on RESET pin
1. Connecting capacitor
In case where the RESET signal rise time is long, connect a ce-
ramic capacitor or others across the RESET pin and the Vss pin.
And use a 1000 pF or more capacitor for high frequency use.
When connecting the capacitor, note the following :
• Make the length of the wiring which is connected to a capacitor
• Be sure to verify the operation of application products on the
<Reason>
If the several nanosecond or several ten nanosecond impulse
noise enters the RESET pin, it may cause a microcomputer fail-
ure.
as short as possible.
user side.
data to the watchdog timer control register to prevent timer un-
derflow.
watchdog timer is running during the oscillation stabilizing time
after the STP instruction is released. In order to avoid the un-
derflow of the watchdog timer, the watchdog timer control
register must be written just before executing the STP instruc-
tion.
timer control register (address 0039
once after releasing reset. After rewriting it is disable to write
any data to this bit.
sion selection bit of the CPU mode register.
The f(X
ing f(X
The on-chip oscillator output is supplied to the watchdog timer
when selecting the on-chip oscillator output as the CPU clock.
sitive to noise when V
voltage, accuracy may become low rather than the case
where V
value..
low temperature may become extremely low compared with
that at room temperature. When the system would be used at
low temperature, the use at V
mended.
IN
IN
) as the CPU clock.
REF
) clock is supplied to the watchdog timer when select-
REF
voltage is lower than [ 3.0 V ], the accuracy at the
voltage and Vcc voltage are set up to the same
REF
voltage is set up lower than Vcc
REF
=3.0 V or more is recom-
16
)) can be rewritten only