C8051F120/1/2/3/4/5/6/7 C8051F130/1/2/3
Rev. 1.4
325
24. Programmable Counter Array
The Programmable Counter Array (PCA0) provides enhanced timer functionality while requiring less CPU
intervention than the standard 8051 counter/timers. PCA0 consists of a dedicated 16-bit counter/timer and
six 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 (See
through 3 and the Priority Crossbar Decoder” on page 238
). The counter/timer is driven by a program-
mable timebase that can select between six inputs as its source: system clock, system clock divided by
four, system clock divided by twelve, the external oscillator clock source divided by 8, Timer 0 overflow, or
an external clock signal on the ECI line. Each capture/compare module may be configured to operate inde-
pendently in one of six modes: Edge-Triggered Capture, Software Timer, High-Speed Output, Frequency
Output, 8-Bit PWM, or 16-Bit PWM (each is described in
). The PCA is configured and con-
trolled through the system controller's Special Function Registers. The basic PCA block diagram is shown
in Figure 24.1.
Figure 24.1. PCA Block Diagram
Capture/Compare
Module 1
Capture/Compare
Module 0
Capture/Compare
Module 2
Capture/Compare
Module 3
CE
X1
EC
I
Crossbar
CE
X2
CE
X3
CE
X0
Port I/O
16-Bit Counter/Timer
PCA
CLOCK
MUX
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
SYSCLK
External Clock/8
Capture/Compare
Module 4
CE
X4
Capture/Compare
Module 5
CE
X5
Summary of Contents for C8051F12 Series
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