229
Bit 2—Transmit End Interrupt Enable (TEIE): Bit 2 enables or disables the transmit end
interrupt (TEI) requested if there is no valid transmit data in TDR when the MSB is transmitted.
Bit 2: TEIE
Description
0
Transmit end interrupt (TEI) disabled
(initial value)
1
Transmit end interrupt (TEI) enabled
*
Note:
*
A TEI interrupt can be cleared by clearing the SSR bit TDRE to 0 and clearing the transmit
end bit (TEND) to 0, or by clearing bit TEIE to 0.
Bits 1 and 0—Clock Enable 1, 0 (CKE1, CKE0): Bits 1 and 0 select the clock source and enable
or disable clock output at pin SCK
3
. The combination of bits CKE1 and CKE0 determines whether
pin SCK
3
is a general I/O port, a clock output pin, or a clock input pin.
Note that the CKE0 setting is valid only when operation is in asynchronous mode using an internal
clock (CKE1 = 0). This bit is invalid in synchronous mode or when using an external clock
(CKE1 = 1). In synchronous mode and in external clock mode, clear CKE0 to 0. After setting bits
CKE1 and CKE0, the operation mode must first be set in the serial mode register (SMR).
See table 10.10 in 10.3.3, Operation, for details on clock source selection.
Description
Bit 1: CKE1
Bit 0: CKE0
Communication Mode
Clock Source
SCK
3
Pin Function
0
0
Asynchronous
Internal clock
I/O port
*
1
Synchronous
Internal clock
Serial clock output
*
1
1
Asynchronous
Internal clock
Clock output
*
2
Synchronous
Reserved
Reserved
1
0
Asynchronous
External clock
Clock input
*
3
Synchronous
External clock
Serial clock input
1
Asynchronous
Reserved
Reserved
Synchronous
Reserved
Reserved
Notes: 1. Initial value
2. A clock is output with the same frequency as the bit rate.
3. Input a clock with a frequency 16 times the bit rate.