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19. SI1CMDR is not used.
20. SI1STR does not need to be read.
21. ConÞgure the SCC1 for HDLC operation (to handle the LAPD protocol of the D
channel), and conÞgure SCC2 and SMC1 as preferred.
22. SI1GMR = 0x01. Enable TDM A (one static TDM).
23. Enable SCC1, SCC2 and SMC1.
14.7 Serial Interface GCI Support
The MPC8260 fully supports the normal mode of the GCI, also known as the ISDN-
oriented modular revision 2.2 (IOM-2), and the SCIT. The MPC8260 also supports the D-
channel access control in S/T interface terminals using the command/indication (C/I)
channel.
The GCI bus consists of four linesÑtwo data lines, a clock, and a frame synchronization
line. Usually, an 8-kHz frame structure deÞnes the various channels within the 256-kbps
data rate. The MPC8260 supports two (limited by the number of SMCs) independent GCI
buses, each with independent receive and transmit sections. The interface can also be used
in a multiplexed frame structure on which up to eight physical layer devices multiplex their
GCI channels. In this mode, the data rate would be 2,048 kbps.
In the GCI bus, the clock rate is twice the data rate. The SI divides the input clock by two
to produce the data clock. The MPC8260 also has data strobe lines and the 1´ data rate
clock L1CLKOx output pins. These signals are used for interfacing devices to GCI that do
not support the GCI bus. Table 14-11 describes GCI signals for each transmit and receive
channel.
Signal
L1RSYNCx
Used as a GCI sync signal; input to the MPC8260. This signal indicates that the clock periods
following the pulse designate the GCI frame.
L1RCLKx
Used as a GCI clock; input to the MPC8260. The L1RCLKx signal frequency is twice the data clock.
L1RXDx
Used as a GCI receive data; input to the MPC8260.
L1TXDx
Used as a GCI transmit data; open-drain output. Valid only for the bits that are supported by the IDL;
otherwise, three-stated.
L1CLKOx
Optional signal; output from the MPC8260. This 1´ clock output is used to clock devices that do not
interface directly to the GCI. If the double-speed clock is used, (DSCx bit is set in the SIxMR), this
output is the L1RCLKx divided by 2; otherwise, it is simply a 1´ output of the L1RCLKx signal.
Note: x = a, b, c, and d for TDMa, TDMb, TDMc, and TDMd (for SI1 and SI2).
The GCI bus signals are shown in Figure 14-24.
MOTOROLA
Table 14-11. GCI Signals
Chapter 14. Serial Interface with Time-Slot Assigner
Part IV. Communications Processor Module
Description
14-31
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