M37544 Datasheet, PDF (37/68 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7544 Group
● Oscillation stop detection circuit
The oscillation stop detection circuit is used for reset occurrence
when a ceramic resonator or an oscillation circuit stops by discon-
nection. When internal reset occurs, reset because of oscillation
stop can be detected by setting “1” to the oscillation stop detection
status bit.
Also, when using the oscillation stop detection circuit, an on-chip
oscillator is required.
Figure 48 shows the state transition.
The oscillation stop detection status bit retains “1”, not initialized,
when the oscillation stop reset occurs. The oscillation stop detec-
tion status bit is initialized to “0” when the external reset occurs.
Accordingly, reset by oscillation stop can be confirmed by using
this bit.
■ Notes on Oscillation Stop Detection Circuit
• Oscillation stop detection status bit is initialized by the following
operation.
(1) External reset
(2) Write “0” data to the ceramic or RC oscillation stop detection
function active bit.
• The oscillation stop detection circuit is not included in the emu-
lator MCU “M37544RSS”.
b7
b0
MISRG(address 003816, initial value: 0016)
Oscillation stabilization time set bit after
release of the STP instruction
0: Set “0116” in timer1, and “FF16”
in prescaler 1 automatically
1: Not set automatically
Ceramic/quartz-crystal or RC oscillation
stop detection function active bit
0: Detection function inactive
1: Detection function active
Reserved bits (return “0” when read)
(Do not write “1” to these bits)
Disable (return “0” when read)
Oscillation stop detection status bit
0: Oscillation stop not detected
1: Oscillation stop detected
Fig. 45 Structure of MISRG
Rev.1.04 2004.06.08 page 37 of 66
REJ03B0012-0104Z