Motorola MPC860 PowerQUICC, User Manual

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23-4 MPC860 PowerQUICC UserÕs Manual MOTOROLA
Part V. The Communications Processor Module
The synchronous UART transmit shift register sends outgoing data on TXDx. Data is then
clocked synchronously with the transmit clock, which can have an internal or external
source.
23.4 SCC UART Parameter RAM
For UART mode, the protocol-speciÞc area of the SCC parameter RAM is mapped as in
Table 23-1.
Table 23-1. UART-Specific SCC Parameter RAM Memory Map
Offset
1
Name Width Description
0x30 Ñ DWord Reserved
0x38 MAX_IDL Hword Maximum idle characters. When a character is received, the receiver begins
counting idle characters. If MAX_IDL idle characters are received before the
next data character, an idle timeout occurs and the buffer is closed, generating
a maskable interrupt request to the core to receive the data from the buffer.
Thus, MAX_IDL offers a way to demarcate frames. To disable the feature, clear
MAX_IDL. The bit length of an idle character is calculated as follows: 1 + data
length (5Ð9) + 1 (if parity is used) + number of stop bits (1Ð2). For 8 data bits,
no parity, and 1 stop bit, the character length is 10 bits.
0x3A IDLC Hword Temporary idle counter. Holds the current idle count for the idle timeout
process. IDLC is a down-counter and does not need to be initialized or
accessed.
0x3C BRKCR Hword Break count register (transmit). Determines the number of break characters the
transmitter sends. The transmitter sends a break character sequence when a
STOP TRANSMIT
command is issued. For 8 data bits, no parity, 1 stop bit, and
1 start bit, each break character consists of 10 zero bits.
0x3E PAREC Hword User-initialized,16-bit (moduloÐ2
16
) counters incremented by the CP.
PAREC counts received parity errors.
FRMEC counts received characters with framing errors.
NOSEC counts received characters with noise errors.
BRKEC counts break conditions on the signal. A break condition can last for
hundreds of bit times, yet BRKEC is incremented only once during that period.
0x40 FRMEC Hword
0x42 NOSEC Hword
0x44 BRKEC Hword
0x46 BRKLN Hword Last received break length. Holds the length of the last received break
character sequence measured in bits but is only accurate to within one
character unit. For example, if RXD
x is low for 20 bit times and the deÞned
character length is 8 bits, BRKLN = 0x0010, indicating that the break sequence
is at least 2 characters long. (BRKLN will register 0x0018 once 24 bits of break
arrive.) For 8 data bits, no parity, 1 stop bit, and 1 start bit, BRKLN is accurate
to within 10 bits.
0x48 UADDR1 Hword UART address character 1/2. In multidrop mode, the receiver provides
automatic address recognition for two addresses. In this case, program the
lower order bytes of UADDR1 and UADDR2 with the two preferred addresses.
0x4A UADDR2 Hword
0x4C RTEMP Hword Temporary storage
0x4E TOSEQ Hword Transmit out-of-sequence character. Inserts out-of-sequence characters, such
as XOFF and XON, into the transmit stream. The TOSEQ character is put in
the Tx FIFO without affecting a Tx buffer in progress. See Section 23.11,
ÒInserting Control Characters into the Transmit Data Stream.Ó