204
Agere Systems Inc.
T8302 Internet Protocol Telephone
Advanced RISC Machine (
ARM
)
Data Sheet
July 2001
15 Synchronous Serial Interface (SSI)
(continued)
15.2.2 SSI Control Register 1
SSI control register 1
is used to enable communication, set up the SSI in master/slave mode, report status, and
configure the clock.
Table 183. SSI Control Register 1
Address 0xE000 4004
Bit #
Name
Bit #
Name
Bit #
31:16
15
31:16
RSVD
11
SDOEN
15
EN
10
14
13
12
MSTR
9
MDOEN
SPOL
8:3
RSVD
SPHA
2:0
SCLK
SSNEN
Name
RSVD
EN
Description
Reserved.
Enable.
Enables or disables the SSI.
If 1, the SSI is enabled.
If 0, it is disabled.
Master mode.
Configures the SSI in master or slave mode.
14
MSTR
If 1, the SSI is configured in master mode.
If 0, it is configured in slave mode.
Idle state.
Determines the idle state of the
SCK
clock.
13
SPOL
If 1, the
SCK
clock is idle at logic 1.
If 0, it is idle at logic 0.
Data change.
Determines when the data changes in each
SCK
cycle.
12
SPHA
If 1, output data is shifted at the leading transition of
SCK
and input data is sampled at the mid-
point transition of
SCK
.
If 0, output data is shifted at the midpoint transition of
SCK
and input data is sampled at the
leading transition of SCK.
Output enable.
Enables output from the
MDISDO
pin if the SSI is configured as a slave.
11
SDOEN
If 1, output from the
MDISDO
pin is enabled if the SSI is configured as a slave.
If 0, output is disabled.
A master SSI device simultaneously broadcasts a message to several slaves as long as no
more than one of the slaves tries to drive the
MDISDO
line. Also, SSI systems that tie
MDOSDI
and
MDISDO
together to form a single bidirectional data line also need to selectively disable
MDISDO
output.
SSN enable.
10
SSNEN
If 1 in master mode, the
SSN
input is enabled and causes a mode fault.
If 0 in master mode, the
SSN
input is disabled.
If 1 in slave mode, the slave uses the
SSN
input to determine if it is selected for operation.
If 0 in slave mode, the slave is not selected for operation.
MDOEN MDOSDI enable.
Enables output from the
MDOSDI
pin if the SSI is configured as master.
9
If 1, output from the
MDOSDI
pin is enabled if the SSI is configured as master.
If 0, output is disabled.
Bit 9 is 0 when the master SSI wants to receive a byte of data from a slave without transmitting
a byte.