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Timer 1 and timer 2 are both 16-bit up/down timer/counters that can be clocked internally or ex-
ternally. Each timer/counter is called a timer if it is clocked internally and a counter if it is clocked
externally. (See Chapter 10, "Event Processor Array (EPA)," for additional information on the
EPA and timer/counters.)
2.5.6
Analog-to-digital Converter
The analog-to-digital (A/D) converter converts an analog input voltage to a digital equivalent.
Resolution is either 8 or 10 bits; sample and convert times are programmable. Conversions can
be performed on the analog ground and reference voltage, and the results can be used to calculate
gain and zero-offset errors. The internal zero-offset compensation circuit enables automatic zero-
offset adjustment. The A/D also has a threshold-detection mode, which can be used to generate
an interrupt when a programmable threshold voltage is crossed in either direction. The A/D scan
mode of the PTS facilitates automated A/D conversions and result storage.
The main components of the A/D converter are a sample-and-hold circuit and an 8-bit or 10-bit
successive approximation analog-to-digital converter. See Chapter 11, "Analog-to-digital Con-
verter," for more information.
2.5.7
Watchdog Timer
The watchdog timer is a 16-bit internal timer that resets the device if the software fails to operate
properly. See Chapter 13, "Minimum Hardware Considerations," for more information.
2.5.8
CAN Serial Communications Controller (87C196CA Only)
The 87C196CA device has a peripheral not found on 8XC196Jx or 8XC196Kx devices, the CAN
(controller area network) peripheral. The CAN serial communications controller manages com-
munications between multiple network nodes. This integrated peripheral is similar to Intel's
standalone 82527 CAN serial communications controller, supporting both the standard and ex-
tended message frames specified by the CAN 2.0 protocol parts A and B. See Chapter 12, "CAN
Serial Communications Controller," for more information.
2.6
SPECIAL OPERATING MODES
In addition to the normal execution mode, the device operates in several special-purpose modes.
Idle and powerdown modes conserve power when the device is inactive. On-circuit emulation
(ONCE) mode electrically isolates the microcontroller from the system, and several other modes
provide programming options for nonvolatile memory. See Chapter 14, "Special Operating
Modes," for more information about idle, powerdown, and ONCE modes and Chapter 16, "Pro-
gramming the Nonvolatile Memory," for details about programming options.
ARCHITECTURAL OVERVIEW
2-11
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