c8051t623-g Silicon Laboratories, c8051t623-g Datasheet - Page 217

• Manufacturer Part Number: c8051t623-g
• Description: Full Speed Usb Eprom Mcu Family
• Manufacturer: Silicon Laboratories

C8051T622/3 and C8051T326/7
24. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU
intervention than the standard 8051 counter/timers. The PCA consists of a dedicated 16-bit counter/timer
and three 16-bit capture/compare modules. Each capture/compare module has its own associated I/O line
(CEXn) which is routed through the Crossbar to Port I/O when enabled. The counter/timer is driven by a
programmable timebase that can select between six sources: system clock, system clock divided by four,
system clock divided by twelve, the external oscillator clock source divided by 8, Timer 0 overflows, or an
external clock signal on the ECI input pin. Each capture/compare module may be configured to operate
independently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Fre-
quency Output, 8 to 11-Bit PWM, or 16-Bit PWM (each mode is described in Section
“24.3. Capture/Compare Modules” on page 227). The external oscillator clock option is ideal for real-time
clock (RTC) functionality, allowing the PCA to be clocked by a precision external oscillator while the inter-
nal oscillator drives the system clock. The PCA is configured and controlled through the system controller's
Special Function Registers. The PCA block diagram is shown in Figure 24.1.
Important Note: The PCA Module 2 may be used as a watchdog timer (WDT), and is enabled in this mode
following a system reset. Access to certain PCA registers is restricted while WDT mode is enabled .
See Section 24.4 for details.
224
S Y S C L K / 1 2
T i m e r 0 O v e r f l o w
S Y S C L K
E x t e r n a l C l o c k / 8
S Y S C L K / 4
E C I
C a p t u r e / C o m p a r e
M o d u l e 0
C L O C K
M U X
P C A
Figure 24.1. PCA Block Diagram
D i g i t a l C r o s s b a r
P o r t I / O
Rev. 1.1
C a p t u r e / C o m p a r e
1 6 - B i t C o u n t e r / T i m e r
M o d u l e 1
C a p t u r e / C o m p a r e
M o d u l e 2 / W D T