Datasheet

56F8355 Technical Data, Rev. 17
112 Freescale Semiconductor
Preliminary
6.5.6.10 Reserved—Bit 6
This bit field is reserved or not implemented. It is read as 0 and cannot be modified by writing.
6.5.6.11 CTRL—Bit 5
This bit controls the pullup resistors on the WR and RD pins.
6.5.6.12 Reserved—Bit 4
This bit field is reserved or not implemented. It is read as 0 and cannot be modified by writing.
6.5.6.13 JTAG—Bit 3
This bit controls the pullup resistors on the TRST, TMS and TDI pins.
6.5.6.14 Reserved—Bit 2–0
This bit field is reserved or not implemented. It is read as 0 and cannot be modified by writing.
6.5.7 CLKO Select Register (SIM_CLKOSR)
The CLKO select register can be used to multiplex out any one of the clocks generated inside the clock
generation and SIM modules. The default value is SYS_CLK. This path has been optimized in order to
minimize any delay and clock duty cycle distortion. All other clocks primarily muxed out are for test
purposes only, and are subject to significant phase shift at high frequencies.
The upper four bits of the GPIOB register can function as GPIO, A[23:20], 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[23:20] 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[23:20]. This can be changed by altering A[23:20], 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
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