EM78P5840N/41N/42N
8-Bit Microcontrollers
7.11.2 IRC Mode
For some applications where timing is not critical or where accurate oscillator
frequencies are not required, using the RC oscillator offers a cost effective oscillator
configuration. The EM78P5840N/41N/42N provides an internal RC mode with default
frequency values of 4M and 2MHz. In IRC mode, the PLLC, XIN, XOUT, and /RESET
pins can be defined as general purpose I/Os. The IRC oscillation frequency can vary
with VDD, temperature and process variations.
Internal RC Drift Rate (Ta=25°C, VDD=5V±5%, VSS=0V)
Drift Rate
Internal
RC Frequency
Temperature
(-40℃~+85°C)
Voltage
Process
Total
(2.3V~5.5V)
4MHz
2MHz
±5%
±5%
±5%
±5%
±4%
±4%
±14%
±14%
Note: Theoretical values are for reference only. Actual values may vary depending on the actual process.
In IRC mode, Port 60, Port 61, and Port 70 are defined as bidirectional I/O. By clearing
P71S in the code option to “0,” the /RESET pin can also be set as input pin (Port 71). In
IRC mode, only two active modes are available, i.e., Normal and Sleep modes. See
Figure 7-11b for more details.
7.11.3 ERIC Mode
In ERIC mode the device has an internal capacitor and an external resistor (connected
to VDD). The internal capacitor functions as a temperature compensator. In order to
obtain a more accurate frequency, a precise resistor is recommended.
Note that the oscillation frequency of the RC oscillator can vary with VDD, temperatore
and process variations. Moreover, the package type and the PCB layout can also affect
the system frequency.
In addition, the package type and the the PCB layout also affects the system frequency.
The applicable frequencies are listed in the following table:
ERIC Mode Frequency Deviation:
Internal C, External R
Frequency Range
4MHz (R=51K)
2MHz (R=100K)
3.5M ~ 4.4M
1.8M ~ 2.2M
44 •
Product Specification (V1.0) 04.25.2006
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
