DSP56303 FREESCALE [Freescale Semiconductor, Inc], DSP56303 Datasheet - Page 185

• Manufacturer Part Number: DSP56303
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

8.6.3 SCI Clock Control Register (SCCR)
The SCCR is a read/write register that controls the selection of clock modes and baud rates for
the transmit and receive sections of the SCI interface. The SCCR is cleared by a hardware
signal.
Freescale Semiconductor
Number
23–16
11–0
Bit
15
14
13
12
TCM
CD7
23
15
7
Bit Name
CD[11–0]
RCM
COD
TCM
SCP
Reserved. Read as 0. Write to 0 for future compatibility.
RCM
CD6
Table 8-5. SCI Clock Control Register (SCCR) Bit Definitions
22
14
6
Reset
Value
0
0
0
0
0
0
Figure 8-4. SCI Clock Control Register (SCCR)
Reserved. Write to 0 for future compatibility.
Transmit Clock Source
Selects whether an internal or external clock is used for the transmitter. If TCM is cleared,
the internal clock is used. If TCM is set, the external clock (from the SCLK signal) is used.
Receive Clock Mode Source
Selects whether an internal or external clock is used for the receiver. If RCM is cleared, the
internal clock is used. If RCM is set, the external clock (from the SCLK signal) is used.
Clock Prescaler
Selects a divide by 1 (SCP is cleared) or divide by 8 (SCP is set) prescaler for the clock
divider. The output of the prescaler is further divided by 2 to form the SCI clock.
The clock output divider is controlled by COD and the SCI mode. If the SCI mode is
synchronous, the output divider is fixed at divide by 2. If the SCI mode is asynchronous,
either:
• If COD is cleared and SCLK is an output (that is, TCM and RCM are both cleared), then
• If COD is set and SCLK is an output, the SCI clock is fed directly out to the SCLK signal.
Clock Divider
Specifies the divide ratio of the prescale divider in the SCI clock generator. A divide ratio
from 1 to 4096 (CD[11–0] = $000 to $FFF) can be selected.
Clock Out Divider
TCM
the SCI clock is divided by 16 before being output to the SCLK signal. Thus, the SCLK
output is a 1
Thus, the SCLK output is a 16
0
0
1
1
SCP
CD5
21
13
5
RCM
DSP56303 User’s Manual, Rev. 2
0
1
0
1
×
clock.
TX Clock
COD
CD4
External
External
Internal
Internal
20
12
4
RX Clock
External
External
Internal
Internal
×
CD11
CD3
baud clock.
19
11
3
Description
Output
SCLK
Input
Input
Input
CD10
CD2
18
10
2
Synchronous/asynchronous
Synchronous/asynchronous
Asynchronous only
Asynchronous only
SCI Programming Model
CD9
CD1
17
9
1
Mode
CD8
CD0
RESET
16
8
0
8-17