Motorola MPC8260 - Manual (Page 703)

MOTOROLA Chapter 26. Serial Management Controllers (SMCs) 26-7
Part IV. Communications Processor Module
To extract data from a partially full receive buffer, issue a CLOSE RXBD command.
0x12 Ñ Hword Rx internal byte count. 2 A down-count value initialized with the MRBLR value and
decremented with every byte the SDMA channels write.
0x14 Ñ Word Rx temp 2 Can be used only by the CP.
0x18 TSTATE Word Tx internal state. 2 Can be used only by the CP.
0x1C Ñ Word Tx internal data pointer. 2 Updated by the SDMA channels to show the next address in
the buffer to be accessed.
0x20 TBPTR Hword TxBD pointer. Points to the next BD for each SMC channel the transmitter transfers data
from when it is in idle state or to the current BD during frame transmission. After reset or
when the end of the table is reached, the CP initializes TBPTR to the TBASE value. Most
applications never need to write TBPTR, but it can be written when the transmitter is
disabled or when no transmit buffer is in use. For instance, after a
STOP TRANSMIT or
GRACEFUL STOP TRANSMIT command is issued and the frame completes its transmission.
0x22 Ñ Hword Tx internal byte count. 2 A down-count value initialized with the TxBD data length and
decremented with every byte the SDMA channels read.
0x24 Ñ Word Tx temp. 2 Can be used only by the CP.
0x28 MAX_IDL Hword Maximum idle characters. (UART protocol-speciÞc parameter) When a character is
received on the line, the SMC starts counting idle characters received. If MAX_IDL idle
characters arrive before the next character, an idle time-out occurs and the buffer closes,
which sends an interrupt request to the core to receive data from the buffer. MAX_IDL
demarcates frames in UART mode. Clearing MAX_IDL disables the function so the
buffer never closes, regardless of how many idle characters are received. An idle
character is calculated as follows: 1 + data length (5 to 14) + 1 (if parity bit is used) +
number of stop bits (1 or 2). For example, for 8 data bits, no parity, and 1 stop bit,
character length is 10 bits.
0x2A IDLC Hword Temporary idle counter. (UART protocol-speciÞc parameter) Down-counter in which the
CP stores the current idle counter value in the MAX_IDL time-out process.
0x2C BRKLN Hword Last received break length. (UART protocol-speciÞc parameter) Holds the length of the
last received break character sequence measured in character units. For example, if the
receive signal is low for 20 bit times and the deÞned character length is 10 bits, BRKLN =
0x002, indicating that the break sequence is at least 2 characters long. BRKLN is
accurate to within one character length.
0x2E BRKEC Hword Receive break condition counter. (UART protocol-speciÞc parameter) Counts break
conditions on the line. A break condition may last for hundreds of bit times, yet BRKEC
increments only once during that period.
0x30 BRKCR Hword Break count register (transmit). (UART protocol-speciÞc parameter) Determines the
number of break characters the UART controller sends. Set when the SMC sends a
break character sequence after a
STOP TRANSMIT command. For 8 data bits, no parity, 1
stop bit, and 1 start bit, each break character is 10 zeros.
0x32 R_MASK Hword Temporary bit mask. (UART protocol-speciÞc parameter)
0x34 Ñ Word SDMA Temp
1 From the pointer value programmed in SMCx_BASE: SMC1_BASE at 0x87FC, SMC2_BASE at IMMR + 0x88FC.
2 Not accessed for normal operation. May hold helpful information for experienced users and for debugging.
Table 26-2. SMC UART and Transparent Parameter RAM Memory Map (Continued)
Offset 1 Name Width Description