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Special Function Register STB (Address 94 H )
Special Function Register SRB (Address 95 H )
MSB
Bit No.
7
94 H
.7
95 H
.7
After reset the contents of the shift register and the receive buffer register are undefined.
The register SSCMOD is used to enable test modes during factory test. It must not be written or
modified during normal operation of the C541U.
Special Function Register SSCMOD (Address 96 H )
MSB
Bit No.
7
96 H
LOOPB TRIO
Bit
Function
LOOPB
SSC loopback enable
This bit should be used for test purposes only.
LOOPB = 0 : The SSC operates as specified.
LOOPB = 1 : The STO output is connected internally via an inverter to the
TRIO
SSC disable tristate mode of SSC inputs
This bit should be used for test purposes only.
TRIO = 0 :
TRIO = 1 :
5-1
All bits of this register are set to 0 after reset. When writing SSCMOD, these
bits must be written with 0.
LSBSM
SSC LSB shift mode
If LSBSM is cleared, the SSC will shift out the MSB of the data first LSB last. If
LSBSM is set, the SSC will shift out LSB first and MSB last.
Semiconductor Group
6
5
4
.6
.5
.4
.6
.5
.4
6
5
4
0
0
SRI input, allowing to check the transfer locally without a second
SSC device.
The SSC operates as specified.
The SSC inputs will be connected to the output latch of the
corresponding port pin. This allows a test of the SSC in slave
mode by simulating a transfer via a program setting the port
latches accordingly.
On-Chip Peripheral Components
3
2
.3
.2
.3
.2
3
2
0
0
6-33
Reset Value : XX H
Reset Value : XX H
LSB
1
0
.1
.0
STB
.1
.0
SRB
Reset Value : 00 H
LSB
1
0
0
LSBSM
SSCMOD
1999-04-01
C541U
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