SST89E54RD View Datasheet(PDF) - Silicon Storage Technology
Part Name
Description
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SST89E54RD Datasheet PDF : 81 Pages
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FlashFlex51 MCU
SST89E52RD2/RD / SST89E54RD2/RD / SST89E58RD2/RD
SST89V52RD2/RD / SST89V54RD2/RD / SST89V58RD2/RD
Data Sheet
8.0 PROGRAMMABLE COUNTER ARRAY
The Programmable Counter Array (PCA) present on the
SST89E/V5xRD2/RD is a special 16-bit timer that has five
16-bit capture/compare modules. Each of the modules can
be programmed to operate in one of four modes: rising
and/or falling edge capture, software timer, high-speed out-
put, or pulse width modulator. The 5th module can be pro-
grammed as a Watchdog Timer in addition to the other four
modes. Each module has a pin associated with it in port 1.
Module 0 is connected to P1.3 (CEX0), module 1 to P1[4]
(CEX1), module 2 to P1[5] (CEX2), module 3 to P1[6]
(CEX3), and module 4 to P1[7] (CEX4). PCA configuration
is shown in Figure 8-1.
PCA. External events associated with modules are shared
with corresponding Port 1 pins. Modules not using the port
pins can still be used for standard I/O.
Each of the five modules can be programmed in any of the
following modes:
• Rising and/or falling edge capture
• Software timer
• High speed output
• Watchdog Timer (Module 4 only)
• Pulse Width Modulator (PWM)
8.1 PCA Overview
PCA provides more timing capabilities with less CPU inter-
vention than the standard timer/counter. Its advantages
include reduced software overhead and improved accuracy.
The PCA consists of a dedicated timer/counter which
serves as the time base for an array of five compare/cap-
ture modules. Figure 8-1 shows a block diagram of the
8.2 PCA Timer/Counter
The PCA timer is a free-running 16-bit timer consisting of
registers CH and CL (the high and low bytes of the count
values). The PCA timer is common time base for all five
modules and can be programmed to run at: 1/6 the oscilla-
tor frequency, 1/2 the oscillator frequency, Timer 0 overflow,
or the input on the ECI pin (P1.2). The timer/counter source
is determined from the CPS1 and CPS0 bits in the CMOD
SFR as follows (see “PCA Timer/Counter Mode Register
(CMOD)” on page 27):
TABLE
CPS1
0
0
1
1
8-1: PCA Timer/Counter Source
CPS0
0
1
0
1
12 Clock Mode
fOSC /12
fOSC /4
Timer 0 overflow
External clock at ECI pin
(maximum rate = fOSC /8)
6 Clock Mode
fOSC /6
fOSC /2
Timer 0 overflow
External clock at ECI pin
(maximum rate = fOSC /4)
T8-1.0 1255
16 Bits
PCA Timer/Counter
16 Bits Each
Module 0
Module 1
Module 2
Module 3
Module 4
FIGURE 8-1: PCA Timer/Counter and Compare/Capture Modules
P1.3/CEX0
P1.4/CEX1
P1.5/CEX2
P1.6/CEX3
P1.7/CEX4
1255 F23.0
©2006 Silicon Storage Technology, Inc.
46
S71255-05-000
5/06
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