Datasheet

Port S
M68HC12B Family Data Sheet, Rev. 9.1
Freescale Semiconductor 209
DDS0 — Data Direction for Port S Bit 0
If the SCI receiver is configured for 2-wire SCI operation, corresponding port S pins are input
regardless of the state of these bits.
DDS1 — Data Direction for Port S Bit 1
If the SCI transmitter is configured for 2-wire SCI operation, corresponding port S pins are output
regardless of the state of these bits.
DDS2 and DDS3 — Data Direction for Port S Bit 2 and Bit 3
These bits are for general-purpose only.
DDS6–DDS4 — Data Direction for Port S Bits 6–4
If the SPI is enabled and expects the corresponding port S pin to be an input, it will be an input
regardless of the state of the DDRS bit. If the SPI is enabled and expects the bit to be an output, it will
be an output only if the DDRS bit is set.
DDS7 — Data Direction for Port S Bit 7
In SPI slave mode, DDS7 has no meaning or effect; the PS7 pin is dedicated as the SS
input. In SPI
master mode, DDS7 determines whether PS7 is an error detect input to the SPI or a general-purpose
or slave select output line.
14.4.3 Pullup and Reduced Drive Register for Port S
Read: Anytime
Write: Anytime
RDPS2 — Reduce Drive of PS7–PS4
0 = Port S output drivers for bits 7–4 operate normally.
1 = Port S output pins for bits 7–4 have reduced drive capability for lower power and less noise.
RDPS1 — Reduce Drive of PS3 and PS2
0 = Port S output drivers for bits 3 and 2 operate normally.
1 = Port S output pins for bits 3 and 2 have reduced drive capability for lower power and less noise.
RDPS0 — Reduce Drive of PS1 and PS0
0 = Port S output drivers for bits 1 and 0 operate normally.
1 = Port S output pins for bits 1 and 0 have reduced drive capability for lower power and less noise.
PUPS2 — Pullup Port S Enable PS7–PS4
0 = No internal pullups on port S bits 7–4.
1 = Port S input pins for bits 7–4 have an active pullup device. If a pin is programmed as output, the
pullup device becomes inactive.
Address: $00DB
Bit 7654321Bit 0
Read: 0
RDPS2 RDPS1 RDPS0
0
PUPS2 PUPS1 PUPS0
Write:
Reset:00000000
= Unimplemented
Figure 14-22. Pullup and Reduced Drive Register for Port S (PURDS)