CS5535-UDCF AMD (ADVANCED MICRO DEVICES), CS5535-UDCF Datasheet - Page 108

• Manufacturer Part Number: CS5535-UDCF
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of CS5535-UDCF

• Operating Temperature (min): 0C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Compliant

5.7
The Programmable Interval Timer (PIT) generates pro-
grammable time intervals from the divided clock of an
external clock signal of a crystal oscillator. The PIT (8254)
has six modes of operation. Figure 5-14 shows the block
diagram of the PIT and its connectivity to the Local bus.
The 8254 is comprised of three independently programma-
ble counters. Each counter is 16 bits wide. A 14.318 MHz
external clock signal (from a crystal oscillator or an external
clock chip) is divided by 12 to generate 1.19 MHz, which is
used as a clocking reference for these three counters.
Each counter is enabled or triggered with its GATE signal.
Based on the counting mode, the counter concerned is
activated by a high level or a low-to-high transition of its
GATE signal.
108
Programmable Interval Timer
Register
Control
Timer 0
31506B
Figure 5-14. PIT Block Diagram
PIT Shadow
GeodeLink™ Adapter
c
Register
Timer 1
Local Bus
CPU
Each counter has its output signal, whose shape is depen-
dent upon the counter’s operational mode. The Control
register loads the counters and controls the various modes
of operation. This Control register controls the operation
mode of the control logic (counter state machine), which in
turn controls the counter, the high-order and low-order out-
put latches. A status latch is also present in the 8254 and is
used to output status information.
Features include:
• Comprised of three 16-bit wide counters.
• Supports read-back and counter latch commands.
• Supports six modes of counting.
• Allows several counter latch commands in parallel with
the read-back command.
AMD Geode™ CS5535 Companion Device Data Book
Divide By 12
Timer 2
Programmable Interval Timer
14 MHz