Motorola MPC8260 - Manual (Page 704)

26-8 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
Certain parameter RAM values must be initialized before the SMC is enabled. Other values
are initialized or written by the CP. Once values are initialized, software typically does not
need to update them because activity centers mostly around transmit and receive BDs rather
than parameter RAM. However, note the following:
¥ Parameter RAM can be read at any time.
¥ Values that pertain to the SMC transmitter can be written only if SMCMR[TEN] is
zero or between the
STOP TRANSMIT and RESTART TRANSMIT commands.
¥ Values for the SMC receiver can be written only when SMCMR[REN] is zero, or, if
the receiver is previously enabled, after an
ENTER HUNT MODE command is issued
but before the CLOSE RXBD command is issued and REN is set.
26.2.3.1 SMC Function Code Registers (RFCR/TFCR)
Each SMC channel has four receive buffers (RFCRn) and four transmit buffers (TFCRn).
The function code registers contain the transaction speciÞcation associated with SDMA
channel accesses to external memory. Figure 26-4 shows the register format.
Table 26-3 describes FCR Þelds.
Bit 0 1 2 3 4 5 6 7
Field GBL BO TC2 DTB Ñ
R/W R/W
Address SMC base + 0x04 (RFCR)/SMC base + 0x05 (TFCR)
Figure 26-4. SMC Function Code Registers (RFCR/TFCR)
Table 26-3. RFCR/TFCR Field Descriptions
Bit Name Description
0Р1 С Reserved, should be cleared.
2 GBL Global access bit
0 Disable memory snooping
1 Enable memory snooping
3Ð4 BO Byte ordering. Selects byte ordering of the data buffer.
00 The DEC/Intel convention (swapped operation or little-endian). The transmission order of bytes
within a buffer word is opposite of Motorola mode. (32-bit port size memory only).
01 PowerPC little-endian. As data is sent onto the serial line from the buffer, the LSB of the buffer
double word contains data to be sent earlier than the MSB of the same double word.
1x Motorola (big-endian) byte ordering (normal operation). As data is sent onto the serial line from the
buffer, the MSB of the buffer word contains data to be sent earlier than the LSB of the same word.
5 TC2 Transfer code 2. Contains the transfer code value of TC[2], used during this SDMA channel memory
access. TC[0Ð1] is driven with a 0b11 to identify this SDMA channel access as a DMA-type access.
6 DTB Data bus indicator.
0 Use 60x bus for SDMA operation.
1 Use local bus for SDMA operation.
7 Ñ Reserved, should be cleared.