Datasheet

56F8357 Technical Data, Rev. 15
114 Freescale Semiconductor
Preliminary
The upper four bits of the GPIOB register can function as GPIO, A[23:A20], or as additional clock output
signals. GPIO has priority and is enabled/disabled via the GPIOB_PER. If GPIOB[7:4] are programmed
to operate as peripheral outputs, then the choice between A[23:A20] and additional clock outputs is done
here in the CLKOSR. The default state is for the peripheral function of GPIOB[7:4] to be programmed as
A[23:A20]. This can be changed by altering A[23:A20] as shown in Figure 6-9.
Figure 6-9 CLKO Select Register (SIM_CLKOSR)
6.5.7.1 Reserved—Bits 15–10
This bit field is reserved or not implemented. It is read as 0 and cannot be modified by writing.
6.5.7.2 Alternate GPIOB Peripheral Function for A23 (A23)—Bit 9
• 0 = Peripheral output function of GPIOB7 is defined to be A23
• 1 = Peripheral output function of GPIOB7 is defined to be the oscillator clock (MSTR_OSC in Figure 3-4)
6.5.7.3 Alternate GPIOB Peripheral Function for A22 (A22)—Bit 8
• 0 = Peripheral output function of GPIOB6 is defined to be A22
• 1 = Peripheral output function of GPIOB6 is defined to be SYS_CLK2
6.5.7.4 Alternate GPIOB Peripheral Function for A21 (A21)—Bit 7
• 0 = Peripheral output function of GPIOB5 is defined to be A21
• 1 = Peripheral output function of GPIOB5 is defined to be SYS_CLK
6.5.7.5 Alternate GPIOB Peripheral Function for A20 (A20)—Bit 6
• 0 = Peripheral output function of GPIOB4 is defined to be A20
• 1 = Peripheral output function of GPIOB4 is defined to be the prescaler clock (FREF in Figure 3-4)
6.5.7.6 Clockout Disable (CLKDIS)—Bit 5
• 0 = CLKOUT output is enabled and will output the signal indicated by CLKOSEL
• 1 = CLKOUT is tri-stated
Base + $A 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Read
0 0 0 0 0 0
A23 A22 A21 A20
CLK
DIS
CLKOSEL
Write
RESET
0 0 0 0 0 0 00001 0 0000