Motorola MC68VZ328 - Manual (Page 88)

5-6 MC68VZ328 User’s Manual
Programming Model
5.2.4 I/O Drive Control Register
This register controls the driving strength of all I/O signals. By default, all pins are defaulted to 4 mA
driving current. After reset, system software should select 2 mA driving for those signals that do not need
high-current driving for power saving. The bit assignments for the register are shown in the following
display. The settings for the bits in the register are listed in Table 5-4.
IODCR I/O Drive Control Register 0x(FF)FFF008
BIT 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 BIT 0
AB DB CB PM PK PJ PG PF PE PD PC PB PA
TYPE rw rw rw rw rw rw rw rw rw rw rw rw rw
RESET
0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1
0x1FFF
Table 5-4. I/O Drive Control Register Description
Name Description Setting
Reserved
Bits 15–13 Reserved Do not use these bits.
AB
Bit 12 Address Bus Signals I/O Drive Control—It should be
noted that A[23:20] are controlled by the PF bit. 0 = I/O drive current for each pin is 2 mA.
1 = I/O drive current for each pin is 4 mA.
DB
Bit 11 Upper Data Bus Signals I/O Drive Control—The
lower data bus is controlled by the PA bit. 0 = I/O drive current for each pin is 2 mA.
1 = I/O drive current for each pin is 4 mA.
CB
Bit 10 Control Bus Signals—Only those signals or functions
not multiplexed with GPIO are controlled by this bit. 0 = I/O drive current for each pin is 2 mA.
1 = I/O drive current for each pin is 4 mA.
PM–PA
Bits 9–0 Port M to Port A Group I/O Drive Control—Each bit
controls the drive current for the lines in the respective
port. 0 = I/O drive current for each pin is 2 mA.
1 = I/O drive current for each pin is 4 mA.