274
11.2
Register Descriptions
11.2.1
DTMF Control Register (DTCR)
Bit
7
6
5
4
3
2
1
0
DTEN
—
CLOE
RWOE
CLF1
CLF0
RWF1
RWF0
Initial value
0
1
0
0
0
0
0
0
Read/Write
R/W
—
R/W
R/W
R/W
R/W
R/W
R/W
DTCR is an 8-bit read/write register that enables the DTMF generator, enables row and column
output, and selects the output frequencies.
Upon reset, DTCR is initialized to H'40.
Bit 7—DTMF Generator Enable (DTEN): Bit 7 enables or disables operation of the DTMF
generator.
Bit 7: DTEN
Description
0
DTMF generator is halted
(initial value)
1
DTMF generator operates
Bit 6—Reserved Bit: Bit 6 is reserved: it is always read as 1, and cannot be modified.
Bit 5—Column Output Enable (CLOE): Bit 5 enables or disables DTMF column signal output.
Bit 5: CLOE
Description
0
DTMF column signal output is disabled (high-impedance)
(initial value)
1
DTMF column signal output is enabled
Bit 4—Row Output Enable (RWOE): Bit 4 enables or disables DTMF row signal output.
Bit 4: RWOE
Description
0
DTMF row signal output is disabled (high-impedance)
(initial value)
1
DTMF row signal output is enabled