MC68HC908AS32A Datasheet, PDF (159/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

Port E
13.6 Port E
Port E is an 8-bit special function port that shares two of its pins with the TIM, two of its pins with the serial
communications interface module (SCI), and four of its pins with the serial peripheral interface module
(SPI).
13.6.1 Port E Data Register
The port E data register contains a data latch for each of the eight port E pins.
Address: $0008
Read:
Write:
Bit 7
PTE7
6
PTE6
5
PTE5
4
PTE4
3
PTE3
2
PTE2
Reset:
Alternative Function: SPSCK
MOSI
MISO
Unaffected by reset
SS
TCH1
TCH0
Figure 13-13. Port E Data Register (PTE)
1
PTE1
RxD
Bit 0
PTE0
TxD
PTE[7:0] — Port E Data Bits
PTE[7:0] are read/write, software programmable bits. Data direction of each port E pin is under the
control of the corresponding bit in data direction register E.
SPSCK — SPI Serial Clock Bit
The PTE7/SPSCK pin is the serial clock input of an SPI slave module and serial clock output of an SPI
master module. When the SPE bit is clear, the PTE7/SPSCK pin is available for general-purpose I/O.
See Chapter 16 Serial Peripheral Interface (SPI).
MOSI — Master Out/Slave In Bit
The PTE6/MOSI pin is the master out/slave in terminal of the SPI module. When the SPE bit is clear,
the PTE6/MOSI pin is available for general-purpose I/O.
MISO — Master In/Slave Out Bit
The PTE5/MISO pin is the master in/slave out terminal of the SPI module. When the SPI enable bit,
SPE, is clear, the SPI module is disabled, and the PTE5/MISO pin is available for general-purpose I/O.
See Chapter 16 Serial Peripheral Interface (SPI).
SS — Slave Select Bit
The PTE4/SS pin is the slave select input of the SPI module. When the SPE bit is clear, or when the
SPI master bit (SPMSTR) is set and MODFEN bit is low, the PTE4/SS pin is available for
general-purpose I/O. See 16.12.4 SS (Slave Select). When the SPI is enabled as a slave, the DDRF0
bit in data direction register E (DDRE) has no effect on the PTE4/SS pin.
NOTE
Data direction register E (DDRE) does not affect the data direction of port
E pins that are being used by the SPI module. However, the DDRE bits
always determine whether reading port E returns the states of the latches
or the states of the pins. See Table 13-5.
MC68HC908AS32A Data Sheet, Rev. 2.0
Freescale Semiconductor
159