7545 datasheet(38/62 Pages) RENESAS

38 / 62 page

Rev.1.06

Mar 07, 2008

Page 38 of 59

REJ03B0140-0106

7545 Group

CLOCK GENERATING CIRCUIT

An oscillation circuit can be formed by connecting a resonator

between XIN and XOUT.

Use the circuit constants in accordance with the resonator

manufacturer's recommended values.

No external resistor is needed between XIN and XOUT since a

feed-back resistor exists on-chip. (An external feed-back resistor

may be needed depending on conditions.)

When the ceramic resonator/quartz-crystal oscillator is used for

the main clock, connect the ceramic resonator/quartz-crystal

oscillator and the external circuit to pins XIN and XOUT at the

shortest distance. A feedback resistor is built in between pins XIN

and XOUT. (An external feed-back resistor may be needed

depending on conditions.)

Oscillation Control

1. Stop mode

When the STP instruction is executed, the internal clock

φ stops

at an “H” level and the XIN oscillator stops. At this time, timer 1

is set to “0316” and prescaler 1 is set to “FF16”when the

oscillation stabilization time set bit after release of the STP

instruction is “0”. On the other hand, timer 1 and prescaler 1 are

not set when the above bit is “1”. Accordingly, set the wait time

fit for the oscillation stabilization time of the oscillator to be

used. When an external interrupt is accepted, oscillation is

restarted but the internal clock

φ remains at “H” until timer 1

underflows. As soon as timer 1 underflows, the internal clock

is supplied. This is because when a ceramic resonator is used,

some time is required until a start of oscillation.

In the stop mode, the voltage drop detection circuit is stopped, so

that the power dissipation is reduced.

2. Wait mode

If the WIT instruction is executed, the internal clock

φ stops at an

“H” level, but the oscillator does not stop. The internal clock

restarts if a reset occurs or when an interrupt is accepted. Since

the oscillator does not stop, normal operation can be started

immediately after the clock is restarted. To ensure that an

interrupt will be accepted to release the STP or WIT state, the

corresponding interrupt enable bit must be set to “1” before the

STP or WIT instruction is executed.

Fig. 41 External circuit of ceramic resonator/quartz-crystal

oscillator

Fig. 42 Structure of CPU mode register

XIN

XOUT

CIN

COUT

M37545

Note: Insert a damping resistor if required.

The resistance will vary depending on the oscillator and the

oscillation drive capacity setting.

Use the value recommended by the maker of the oscillator.

Also, if the oscillator manufacturer’s data sheet specifies

that a feedback resistor be added external to the chip

though a feedback resistor exists on-chip, insert a feedback

resistor between XIN and XOUT following the instruction.

Processor mode bits (Note)

b1 b0

0 Single-chip mode

Not available

Note : The bit can be rewritten only once after releasing reset.

After rewriting, it is disabled to write any data to this bit.

However, by reset the bit is initialized and can be rewritten, again.

It is not disabled to write any data to this bit for emulator MCU “M37545RLSS.”

CPU mode register

(CPUM: address 003B16, initial value: 8016)

Stack page selection bit

0: 0 page

1: 1 page

Clock division ratio selection bits

b7 b6

0 : Not available

1 : Not available

10 : f(

φ) = f(XIN)/4

1 : Not available

Not used (returns “0” when read)

7545 Datasheet(PDF) 38 Page - Renesas Technology Corp

7545 Datasheet(HTML) 38 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62

Datasheet Download

Link URL