M37542F8FP#U0 Renesas Electronics America, M37542F8FP#U0 Datasheet - Page 71

• Manufacturer Part Number: M37542F8FP#U0
• Description: IC 740 MCU FLASH 32K 36SSOP
• Manufacturer: Renesas Electronics America
• Series: 740/38000r

Specifications of M37542F8FP#U0

• Core Processor: 740
• Core Size: 8-Bit
• Speed: 8MHz
• Connectivity: SIO, UART/USART
• Peripherals: 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: Lead free / RoHS Compliant
• Eeprom Size: -

7542 Group
Fig. 87 Selection of packages
(2) Wiring for RESET pin
Make the length of wiring which is connected to the RESET pin as
short as possible. Especially, connect a capacitor across the
RESET pin and the V
(within 20mm).
<Reason>
The width of a pulse input into the RESET pin is determined by the
timing necessary conditions. If noise having a shorter pulse width
than the standard is input to the RESET pin, the reset is released
before the internal state of the microcomputer is completely initial-
ized. This may cause a program runaway.
Fig. 88 Wiring for the RESET pin
Rev.3.03
REJ03B0006-0303
NOTES ON USE
Countermeasures against noise
1. Shortest wiring length
(1) Package
Select the smallest possible package to make the total wiring
length short.
<Reason>
The wiring length depends on a microcomputer package. Use of a
small package, for example QFP and not DIP, makes the total wir-
ing length short to reduce influence of noise.
DIP
Reset
circuit
Jul 11, 2008
V
SS
SS
SDIP
pin with the shortest possible wiring
Reset
circuit
O.K.
N.G.
Noise
V
Page 69 of 117
SS
SOP
RESET
RESET
V
V
SS
SS
QFP
Fig. 90 Wiring for CNVss pin
(3) Wiring for clock input/output pins
• Make the length of wiring which is connected to clock I/O pins as
• Make the length of wiring (within 20 mm) across the grounding
• Separate the V
<Reason>
If noise enters clock I/O pins, clock waveforms may be deformed.
This may cause a program failure or program runaway. Also, if a
potential difference is caused by the noise between the V
of a microcomputer and the V
clock will not be input in the microcomputer.
Fig. 89 Wiring for clock I/O pins
(4) Wiring to CNVss pin
Connect the CNVss pin to the Vss pin with the shortest possible
wiring.
In the normal microcomputer mode, disconnect a wiring of a serial
rewrite circuit, which is for the flash memory version, from the
MCU by a jumper switch.
<Reason>
The processor mode of a microcomputer is influenced by a poten-
tial at the CNVss pin. If a potential difference is caused by the
noise between pins CNVss and Vss, the processor mode may be-
come unstable. This may cause a microcomputer malfunction or a
program runaway.
A wiring of a serial rewrite circuit may function as an antenna
which feeds noise into the microcomputer.
short as possible.
lead of a capacitor which is connected to an oscillator and the
V
terns.
SS
CNV
V
pin of a microcomputer as short as possible.
SS
SS
N . G .
N o i s e
N.G.
SS
Noise
pattern only for oscillation from other V
X
X
V
IN
OUT
SS
C N V
SS
O.K.
V
S S
S S
level of an oscillator, the correct
F l a s h m e m o r y v e r s i o n
O.K.
O . K .
C N V
X
X
V
IN
OUT
SS
V
S S
S S
J u m p e r s w i t c h
SS
SS
level
S e r i a l
r e w r i t e
c i r c u i t
pat-