Serial Management Controllers (SMCs)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
29-7
To extract data from a partially full Rx buffer, issue a
CLOSE
RXBD
command.
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 Tx and Rx 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.
29.2.3.1
SMC Function Code Registers (RFCR/TFCR)
Each SMC channel has two function code registers—one for receiving (RFCRn) and one for transmitting
(TFCRn). The function code entry contains the value to appear on the function code pins AT[1–3] when
the associated SDMA channel accesses memory. The FCRs also control byte-ordering. See
Figure 29-4
.
Table 29-3
describes RFCR fields.
0x28
—
Hword First half-word of protocol-specific area.
0x32
—
Hword Last half-word of protocol-specific area.
1
From SMC base address. SMC base = IMMR + 3E80 (SMC1), 3F80 (SMC2).
2
Not accessed for normal operation. May hold helpful information for experienced users and for debugging.
0
7
R/W
R/W
Addr
SMC base + 0x04 (RFCR)/SMC base + 0x05 (TFCR)
Figure 29-4. SMC Function Code Registers (RFCR/TFCR)
Table 29-3. RFCR/TFCR Field Descriptions
Bit
Name
Description
0–2
—
Reserved, should be cleared.
3–4
BO
Byte ordering. Set BO to select the required byte ordering for the buffer. If BO is changed on-the-fly,
it takes effect at the beginning of the next frame (Ethernet, HDLC, and transparent) or at the
beginning of the next BD. See
Appendix A, “Byte Ordering.”
00 Reserved
01 Modified little-endian.
1x Big-endian or true little-endian.
5–7
AT[1–3]
Address type 1–3. Contains the user-defined function code value used during the SDMA channel
memory access. AT[0] is always driven high to identify this channel access as a DMA-type access.
Table 29-2. SMC UART and Transparent Parameter RAM Memory Map (continued)
Offset
1
Name
Width
Description
Summary of Contents for PowerQUICC MPC870
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