Programmable Clock and Framing
11-63
Multichannel Buffered Serial Ports
Table 11–17. Receive Frame Synchronization Selection
DLB
in SPCR
FSR
in PCR
GSYNC
in SRGR
Source of Receive Frame
Synchronization
FSR Pin Function
0
0
X
External frame sync signal drives
the FSR input pin, whose signal is
then inverted as determined by
FSRP before being used as
FSR_int.
Input
0
1
0
Sample rate generator frame
sync signal (FSG) drives
FSR_int, FRST = 1.
Output. FSG is inverted as deter-
mined by FSRP before being
driven out on the FSR pin.
0
1
1
Sample rate generator frame
sync signal (FSG) drives
FSR_int, FRST = 1.
Input. The external frame sync
input on FSR is used to synchro-
nize CLKG and generate FSG.
1
0
0
FSX_int drives FSR_int. FSX is
selected as shown in Table 11–18.
High impedance
1
X
1
FSX_int drives FSR_int and is
selected as shown in Table 11–18.
Input. External FSR is not used for
frame synchronization but is used
to synchronize CLKG and gener-
ate FSG since GSYNC = 1.
1
1
0
FSX_int drives FSR_int and is
selected as shown in Table 11–18.
Output. Receive (same as transmit)
frame synchronization is inverted
as determined by FSRP before be-
ing driven out.
11.5.3.3 Transmit Frame Sync Signal Selection: FSXM, FSGM
Table 11–18 shows how you can select the source of transmit frame synchro-
nization pulses. The three choices are:
-
External frame sync input
-
The sample rate generator frame sync signal, FSG
-
A signal that indicates a DXR-to-XSR copy has been made