Serial Interface
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
20-15
20.2.3.8
SI RAM Programming Example
This section shows how to program the SI RAM to support the 10-bit IDL bus whose format is shown in
Figure 20-26
. Here, the TSA supports the B1 channel with SCC2, the D channel with SCC3, the first 4 bits
of the B2 channel with an external device (using a strobe to enable the external device), and the last 4 bits
of B2 with SMC1. Additionally, the TSA marks the D channel with another strobe signal.
Partition the frame from the beginning (the sync) to the end according to the support needed:
•
8 bits (B1)—SCC2
•
1 bit (D)—SCC3 + strobe1
•
1 bit—No support
•
4 bits (B2)—strobe2
•
4 bits (B2)—SMC1
•
1 bit (D)—SCC3 + strobe1
Each partition represents one SI RAM entry.
Table 20-3
shows the SI RAM entries.
Because the IDL requires the same routing for both receiving and sending, the above entries should be
written to both the Rx and Tx route RAM. Set SIMODE[CRTx] (common receive/transmit) to instruct the
TSA to use the same clock and sync for both sets of SI RAM entries.
For examples showing register programming, see
Section 20.2.5.2, “Programming the IDL Interface,”
and
Section 20.2.6.3, “GCI Interface (SCIT Mode) Programming Example.”
20.2.4
The SI Registers
The following sections describe the SI registers.
20.2.4.1
SI Global Mode Register (SIGMR)
The SI global mode register (SIGMR), shown in
Figure 20-12
, defines the SI RAM division modes and
enables the individual TDM channels.
Table 20-3. Example SI RAM Entry Settings for an IDL Bus
Entry
Number
SI RAM
SWTR
SSEL
CSEL
CNT
BYT
LST
Description
1
0
0000
010
0000
1
0
8 bits SCC2 (B1)
2
0
0001
011
0000
0
0
1 bit SCC3 strobe1 (D)
3
0
0000
000
0000
0
0
1 bit no support
4
0
0010
000
0011
0
0
4 bits strobe2 (B2)
5
0
0000
101
0011
0
0
4 bits SMC1 (B2)
6
0
0001
011
0000
0
1
1 bit SCC3 strobe1
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