
Philips Semiconductors
PNX15xx Series
Volume 1 of 1
Chapter 4: Reset
PNX15XX_SER_3
Koninklijke Philips Electronics N.V. 2006. All rights reserved.
Product data sheet
Rev. 3 — 17 March 2006
4-5
The following
Figure 2 pictures the events.
2.2.2
The Interrupt Mode
In this mode, the watchdog timer generates rst an interrupt to the TM3260 before a
PNX15xx Series system reset is generated (when a time-out occurs because the
TM3260 does not answer in time to the interrupt). The sequence of operations is
similar to the non interrupt mode.
First TM3260 CPU writes a value different than 0x0 to the WATCHDOG_COUNT
MMIO register. This starts an internal counter from the value 0x0. When the internal
counter reaches the WATCHDOG_COUNT value an interrupt, SOURCE 42 (see
started. If this second counter reaches the value previously stored into the
INTERRUPT_COUNT MMIO register then a PNX15xx Series system reset is
asserted. The reset follows then the regular software reset timing,
Section 3.2. If the
TM3260 CPU clears the pending interrupt by writing to the INTERRUPT_CLEAR
MMIO register, then the PNX15xx Series system reset is not generated.
The following summarizes the sequence of operations
1. Enable the watchdog interrupt. This includes proper set-up of TM3260 internal
interrupt controller[1] as well as an enable of the INTERRUPT_ENABLE MMIO
register.
2. Initialize the INTERRUPT_COUNT MMIO register with the maximum interrupt
latency authorized before a PNX15xx Series reset is asserted.
3. Start the rst counter by writing a nonzero value to the WATCHDOG_COUNT
MMIO register.
4. A write with 0x0 value to the WATCHDOG_COUNT MMIO register will stop the
count. However this is not intended to be used as such.
Remark: A write of any nonzero value other than the current value will reset the count.
However this is not intended to be used as such.
Figure 2:
Watchdog in Non Interrupt Mode
sys_rst_out_n
//
clk_dtl_mmio
0FF
FE
FD
0
12
3
Watchdog_count
4
5
watchdog_reset
peri_rst_n
SYS_RST_OUT_N
//
1
2
3
4
1: The watchdog count register is programmed
2: The count is happening
3: The count reaches the programmed value and a watchdog reset is issued
4: Both the internal and the external resets are asserted