PIC16F720_13 Datasheet, PDF (69/254 Pages) Microchip Technology – 20-Pin Flash Microcontrollers

7.6 External Clock Modes
7.6.1 EC MODE
The External Clock (EC) mode allows an externally
generated logic level as the system clock source. When
operating in this mode, an external clock source is
connected to the CLKIN input and the CLKOUT is
available for general purpose I/O. Figure 7-2 shows the
pin connections for EC mode.
FIGURE 7-2:
EXTERNAL CLOCK (EC)
MODE OPERATION
Clock from
Ext. System
I/O
CLKIN
PIC^® MCU
CLKOUT
PIC16(L)F720/721
TABLE 7-1: SUMMARY OF REGISTERS ASSOCIATED WITH CLOCK SOURCES
Name Bit 7 Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Register
on Page
OSCCON
—
—
IRCF1 IRCF0
ICSL
ICSS
—
—
67
OSCTUNE —
—
TUN5
TUN4
TUN3 TUN2 TUN1 TUN0
68
Legend: x = unknown, u = unchanged, – = unimplemented locations read as ‘0’. Shaded cells are not used by
oscillators.
TABLE 7-2: SUMMARY OF CONFIGURATION WORD WITH CLOCK SOURCES
Name Bits Bit -/7
Bit -/6
Bit 13/5 Bit 12/4 Bit 11/3 Bit 10/2 Bit 9/1
Bit 8/0
Register
on Page
13:8 —
CONFIG1
7:0 —
—
—
PLLEN
—
— BOREN1 BOREN0
72
CP
MCLRE PWRTE WDTEN
—
FOSC1 FOSC0
13:8 —
—
—
—
—
—
—
—
CONFIG2
73
7:0 —
—
—
—
—
—
WRT1 WRT0
Legend: — = unimplemented location, read as ‘0’. Shaded cells are not used by clock sources.
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DS41430D-page 69