Motorola MPC860 PowerQUICC, User Manual

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MOTOROLA Chapter 22. Serial Communications Controllers 22-7
Part V. The Communications Processor Module
Table 22-2 describes GSMR_L Þelds.
Table 22-2. GSMR_L Field Descriptions
Bit Name Description
0 SIR Serial infrared encodingÑfor SCC2 only. Setting SIR activates the serial infrared coder/encoder. See
Section 26.18, ÒIrDA Encoder/Decoder (SCC2 Only).Ó
1Ð2 EDGE Clock edge. Determines the clock edge the DPLL uses to adjust the receive sample point due to jitter
in the received signal. Ignored in UART protocol or if the 1x clock mode is selected in RDCR.
00 Both the positive and negative edges are used for changing the sample point (default).
01 Positive edge. Only the positive edge of the received signal is used to change the sample point.
10 Negative edge. Only the negative edge of the received signal is used to change the sample point.
11 No adjustment is made to the sample point.
3 TCI Transmit clock invert.
0 Normal operation.
1 Before it is used, the internal Tx clock (TCLK) is inverted by the SCC so it can clock data out
one-half clock earlier (on the rising rather than the falling edge). In this case, the SCC offers a
minimum and maximum rising clock edge-to-data speciÞcation. Data output by the SCC after the
rising edge of an external Tx clock can be latched by the external receiver one clock cycle later on
the next rising edge of the same Tx clock. Recommended for Ethernet, HDLC, and transparent
operation when clock rates exceed 8 MHz to improve data setup time for the external transceiver.
4Ð5 TSNC Transmit sense. Determines the amount of time the internal carrier sense signal stays active after the
last transition on RXD, indicating that the line is free. For instance, AppleTalk can use TSNC to avoid
a spurious CS-changed (SCCE[DCC]) interrupt that would otherwise occur during the frame sync
sequence before the opening ßags. If RDCR is conÞgured to 1
´
clock mode, the delay is the greater
of the two numbers listed. If RDCR is conÞgured to 8
´
, 16
´
, or 32
´
mode, the delay is the smaller
number.
00 InÞnite. Carrier sense is always active (default).
01 14- or 6.5-bit times as determined by RDCR.
10 4- or 1.5-bit times as determined by RDCR (normally for AppleTalk).
11 3- or 1-bit times as determined by RDCR.
6 RINV DPLL Rx input invert data. Must be zero in HDLC bus mode or asynchronous UART mode.
0 Do not invert.
1 Invert data before sending it to the DPLL for reception. Used to produce FM1 from FM0 and NRZI
space from NRZI mark or to invert the data stream in regular NRZ mode.
7 TINV DPLL Tx input invert data. Must be zero in HDLC bus mode.
0 Do not invert.
1 Invert data before sending it to the DPLL for transmission. Used to produce FM1 from FM0 and
NRZI space from NRZI mark and to invert the data stream in regular NRZ mode. In T1 applications,
setting TINV and TEND creates a continuously inverted HDLC data stream.
8Ð10 TPL Tx preamble length. Determines the length of the preamble conÞgured by the TPP bits.
000 No preamble (default).
001 8 bits (1 byte).
010 16 bits (2 bytes).
011 32 bits (4 bytes).
100 48 bits (6 bytes). Select this setting for Ethernet operation.
101 64 bits (8 bytes).
110 128 bits (16 bytes).
111 Reserved.