Philips CEM2100/00, Service Manual

Page: 154 / 430

Page 32
2. Operational Description
2.3 Reset Circuit
T
5CL8
2.3.2 Address trap reset
If the CPU should start looping for some cause such as noise and an attempt be made to fetch an instruction
from the on-chip RAM (when WDTCR1<ATAS> is set to “1”), DBR or the SFR area, address trap reset will be
generated. The reset time is maximum 24/fc[s] (1.5
µ
s at 16.0 MHz).
Note:The operating mode under address trapped is alternative of reset or interrupt. The address trap area is alter-
native.
Note 1: Address “a” is in the SFR, DBR or on-chip RAM (WDTCR1<ATAS> = “1”) space.
Note 2: During reset release, reset vector “r” is read out, and an instruction at address “r” is fetched and decoded.
Figure 2-16 Address Trap Reset
2.3.3 Watchdog timer reset
Refer to Section “Watchdog Timer”.
2.3.4 System clock reset
If the condition as follows is detected, the system clock reset occurs automatically to prevent dead lock of the
CPU. (The oscillation is continued without stopping.)
- In case of clearing SYSCR2<XEN> and SYSCR2<XTEN> simultaneously to
“
0
”
.
- In case of clearing SYSCR2<XEN> to
“
0
”
, when the SYSCR2<SYSCK> is
“
0
”
.
- In case of clearing SYSCR2<XTEN> to
“
0
”
, when the SYSCR2<SYSCK> is
“
1
”
.
The reset time is maximum 24/fc (1.5
µ
s at 16.0 MHz).
Instruction at address r
16/fc [s] maximum 24/fc [s]
Instruction
execution
Internal reset
JP a
Reset release
Address trap is occurred
4/fc to 12/fc [s]