Freescale Semiconductor MPC8260 - Manual (Page 819)

Serial Management Controllers (SMCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 27-7
To extract data from a partially full receive 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 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.
0x24 — Word Tx temp. 2 Can be used only by the CP.
0x28 MAX_IDL Hword Maximum idle characters. (UART protocol-specific 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-specific 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-specific 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 defined 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-specific 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-specific 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-specific parameter)
0x34 — Word SDMA Temp
1
From the pointer value programmed in SMC x _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 27-2. SMC UART and Transparent Parameter RAM Memory Map (continued)
Offset
1
Name Width Description