isppac-powr1208p1 Lattice Semiconductor Corp., isppac-powr1208p1 Datasheet - Page 15

• Manufacturer Part Number: isppac-powr1208p1
• Description: In-system Programmable Power Supply Sequencing Controller And Precision Monitor
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
Clock and Timer Systems
Figure 3-5 shows a block diagram of the ispPAC-POWR1208P1’s internal clock and timer systems. The PLD clock
can be programmed with eight different frequencies based on the internal oscillator frequency of 1MHz.
Figure 3-5. Clock and Timer Block
The internal oscillator runs at a fixed frequency of 1 MHz. This signal is used as a source for the PLD clock pres-
caler, the timer clock prescaler, and also for synchronizing the comparator outputs and clocking the digital filters in
the voltage monitor circuits. Figure 5 shows a functional block diagram of the ispPAC-POWR1208P1’s internal
clock system. The ispPAC-POWR1208P1 can operate from either its own internal or an external supplied clock
source. When the device is configured to use the internal clock source (Schematically, INT/EXT select switch is in
upper position), the CLK pin operates as an output. The user may select either the 1MHz internal clock, or the out-
put of the PLD clock prescaler to be driven out of this pin (1MHz/Prescaler select switch). When the device is con-
figured to use the external clock source (INT/EXT select switch is in lower position), the CLK pin is configured as an
input, and the externally applied clock signal is routed to all prescalers, synchronizers, and other internal functions.
The ispPAC-POWR1208P1 provides prescalers to provide for flexibility in selecting the PLD clock and wide
dynamic range for the timers. The frequencies available for the PLD clock will be the external clock frequency
divided by the chosen prescaler value (listed in Table 3-3).
CLK
Internal
1MHz
OSC
INT/EXT
Select
1MHz/Prescaler
Select
3-15
(Time Out Range)
Timer Prescaler
PLD Clock
Prescaler
Digital Filters
Samplers
VMON
and
To
ispPAC-POWR1208P1 Data Sheet
Timer1
Timer2
Timer3
Timer4