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| 型号： | 935261475512 |
| 厂商： | NXP SEMICONDUCTORS |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | 8 CHANNEL(S), 500K bps, SERIAL COMM CONTROLLER, PQCC84 |
| 封装： | PLASTIC, MO-047AF, SOT-189-3, LCC-84 |
| 文件页数： | 15/59页 |
| 文件大小： | 383K |
| 代理商： | 935261475512 |
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Philips Semiconductors
Product specification
SC28L198
Octal UART for 3.3V and 5V supply voltage
1999 Jan 14
22
Table 8. CR – Command Register
CR is used to write commands to the Octal UART.
Bits 7:3
Bit 2
Bit 1
Bit 0
Channel Com-
mand codes
see “Command
Register Table”
Lock TxD and
RxFIFO en-
ables
Enable Tx
Enable Rx
CR[2] – Lock TxD and RxFIFO enables
If set, the transmitter and receiver enable bits, CR[1:0] are not
significant. The enabled/disabled state of a receiver or transmitter
can be changed only if this bit is at zero during the time of the write
to the command register. WRITES TO THE UPPER BITS OF THE
CR WOULD USUALLY HAVE CR[2] AT 1 to maintain the condition
of the receiver and transmitter. The bit provides a mechanism for
writing commands to a channel, via CR[7:3], without the necessity of
keeping track of or reading the current enable status of the receiver
and transmitter.
CR[1] – Enable Transmitter
A one written to this bit enables operation of the transmitter. The
TxRDY status bit will be asserted. When disabled by writing a zero
to this bit, the command terminates transmitter operation and resets
the TxRDY and TxEMT status bits. However, if a character is being
transmitted or if characters are loaded in the TxFIFO when the
transmitter is disabled, the transmission of the all character(s) is
completed before assuming the inactive state.
CR[0] – Enable Receiver
A one written to this bit enables operation of the receiver. If not in
the special wake up mode, this also forces the receiver into the
search for start bit state. If a zero is written, this command
terminates operation of the receiver immediately – a character being
received will be lost. The command has no effect on the receiver
status bits or any other control registers. If the special wake–up
mode is programmed, the receiver operates even if it is disabled
(see Wake–up Mode).
CR[7:3] – Miscellaneous Commands ( See Table below)
The encoded value of this field can be used to specify a single
command as follows:
00000
No command.
00001
Reserved
00010
Reset receiver. Resets the receiver as if a hardware reset
had been applied. The receiver is disabled and the FIFO
pointer is reset to the first location effectively discarding all
unread characters in the FIFO.
00011
Reset transmitter. Resets the transmitter as if a hardware
reset had been applied.
00100
Reset error status. Clears the received break, parity error,
framing error, and overrun error bits in the status register
(SR[7:4]). Used in character mode to clear overrun error
status (although RB, PE and FE bits will also be cleared),
and in block mode to clear all error status after a block of
data has been received.
00101
Reset break change interrupt. Causes the break detect
change bit in the interrupt status register (ISR[2]) to be
cleared to zero.
00110
Start break. Forces the TxD output low (spacing). If the
transmitter is empty, the start of the break condition will be
delayed up to two bit times. If the transmitter is active, the
break begins when transmission of the current character
is completed. If there are characters in the TxFIFO, the
start of break is delayed until those characters, or any
others loaded after it have been transmitted (TxEMT must
be true before break begins). The transmitter must be
enabled to start a break.
00111
Stop break. The TxD line will go high (marking) within two
bit times. TxD will remain high for one bit time before the
next character, if any, is transmitted.
01000
Assert RTSN. Causes the RTSN output to be asserted
(low).
01001
Negate RTSN. Causes the RTSN output to be negated
(high).
Note: The two commands above actually reset and
set, respectively, the I/O2 or I/O1 pin associated with
the I/OPIOR register.
01010
Reserved
01011
Reserved
01100
Reserved
01101
Block error status mode. Upon reset of the device or an
individual receiver, the block mode of receiver error status
accumulates as each character moves to the bottom of
the RxFIFO, the position from which it will be read. In this
mode of operation, the RxFIFO may contain a character
with non–zero error status for some time. The status will
not reflect the error character’s presence until it is ready to
be popped from the RxFIFO. Command 01101 allows the
error status to be updated as each character is pushed
into the RxFIFO. This allows the earliest detection of a
problem character, but complicates the determination of
exactly which character is causing the error. This mode of
block error accumulation may be exited only by resetting
the chip or the individual receiver.
01111
Reserved.
10000
Transmit an Xon Character
10001
Transmit an Xoff Character
10010
Reserved for channels b–h, for channel a: enables a
Gang Write of Xon Character Registers. After this
command is issued, a write to the channel A Xon
Character Register will result in a write to all channel’s
Xon character registers. This command provides a
mechanism to initialize all the Xon Character registers
with one write. A write to channel A Xon Character
Register returns the Octal UART to the individual Xon
write mode.
10011
Reserved for channels b–h, for channel a: enables Gang
Write of Xoff Character Registers. After this command is
issued, a write to the channel A Xoff Character Register
will result in a write to all channel’s Xoff character
registers. This command provides a mechanism to
initialize all the Xoff Character registers with one write. A
write to channel A Xoff Character Register returns the
Octal UART to the individual Xoff write mode.
Note: Gang writing of Xon/Xoff Character Commands: Issuing
command causes the next write to Xon/Xoff Character Register
A to effect a simultaneous write into the other 3 Xon/Xoff
character registers. After the Xon/Xoff Character Register A is
written, the 28L198 returns to individual write mode for the
Xon/Xoff Character Registers. Other intervening reads and
writes are ignored. The device resets to individual write mode.
10100 Reserved for channels b-h, for channel a: executes a Gang
Load of Xon Character Registers. Executing this
command causes a write of the value x’11 to all channel’s
Xon character registers. This command provides a
mechanism to initialize all the Xon Character registers to a
default value with one write. Execution of this command
is immediate and does not effect the timing of subsequent
host I/O operations.
10101
Reserved for channels b-h, for channel a: executes a
Gang Load of Xoff Character Registers. Executing this
command causes a write of the value x’13 to all channel’s
Xoff character registers. This command provides a
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