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Serial Interface with Time Slot Assigner
MC68360 USER’S MANUAL
CRTx bits, and program the GRx bits to transfer the D channel grant to the SCC that sup-
ports this channel. The user should mark the received bit, which is the grant bit, by program-
ming the channel select bits of the SI RAM to 111 for an internal assertion of a strobe on this
bit. This bit will be sampled by the SI and transferred to the D channel SCC as the grant.
The bit is generally bit 4 of the C/I in channel 2 of GCI, but any other bit may be selected
using the SI RAM.
For example, assuming SCC1 is connected to the D channel, SCC2 is connected to the B1
channel, and SCC4 is connected to the B2 channel, SMC1 is used to handle the C/I chan-
nels, and the D channel grant is on bit 4 of the C/I on SCIT channel 2, the initialization se-
quence is as follows:
1. Program the SI RAM. Write all entries that are not used with $0001, setting
the LST bit and disabling the routing function.
NOTE
Since GCI requires the same routing for both receive and trans-
mit, an exact duplicate of the above entries should be written to
both the receive and transmit sections of the SI RAM beginning
at addresses 0 and 128, respectively.
2. SIMODE = $000080E0. Only TDMa is used; SMC1 is connected. SCIT mode is
used in this example.
NOTE
If SCIT mode is not used, delete the last three entries of the SI
RAM and set the LST bit in the new last entry.
3. SICR = $400040C0. SCC4, SCC2, and SCC1 are connected to the TSA. SCC1
supports the grant mechanism since it is on the D channel.
4. PAODR bit 6 = 1. Configures L1TXDa to an open-drain output.
5. PAPAR bits 6, 7, and 8 = 1. Configures L1TXDa, L1RXDa, and L1RCLKa.
6. PADIR bits 6 and 7 = 1. PADIR bit 8 = 0. Configures L1TXDa, L1RXDa, and
L1RCLKa.
Entry
RAM Word
No.
SWTR
SSEL
CSEL
CNT
BYT
LST
Description
1
0
0000
010
0000
1
0
8 Bits SCC2
2
0
0000
100
0000
1
0
8 Bits SCC4
3
0
0000
101
0000
1
0
8 Bits SMC1
4
0
0000
001
0001
0
2 Bits SCC1
5
0
0000
101
0101
0
6 Bits SMC1
6
0
0000
000
0110
1
0
Skip 7 Bytes
7
0
0000
000
0001
0
Skip 2 Bits
8
0
0000
111
0000
0
1
D Grant Bit
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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