sc16c852 NXP Semiconductors, sc16c852 Datasheet - Page 27

• Manufacturer Part Number: sc16c852
• Description: 2.5 V To 3.3 V Dual Uart, 5 Mbit/s Max. With 128-byte Fifos, Infrared Irda And 16 Mode Or 68 Mode Bus Interface
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SC16C852_1
Product data sheet
7.3.1.1 Mode 0 (FCR bit 3 = 0)
7.3.1.2 Mode 1 (FCR bit 3 = 1)
7.3.1 DMA mode
7.3.2 FIFO mode
7.3 FIFO Control Register (FCR)
This register is used to enable the FIFOs, clear the FIFOs, set the receive FIFO trigger
levels, and select the DMA mode.
In this mode, Transmit Ready (TXRDY) will go to a logic 0 whenever the FIFO (THR, if
FIFO is not enabled) is empty. Receive Ready (RXRDY) will go to a logic 0 whenever the
Receive Holding Register (RHR) is loaded with a character.
In this mode, the Transmit Ready (TXRDY) is set when the transmit FIFO is below the
programmed trigger level. The Receive Ready (RXRDY) is set when the receive FIFO fills
to the programmed trigger level. However, the FIFO continues to fill regardless of the
programmed level until the FIFO is full. RXRDY remains a logic 0 as long as the FIFO fill
level is above the programmed trigger level.
Table 12.
Bit
7:6
5:4
3
Symbol
FCR[7:6]
FCR[5:4]
FCR[3]
FIFO Control Register bits description
Description
Receive trigger level in 32-byte FIFO mode
These bits are used to set the trigger levels for receive FIFO interrupt and
flow control. The SC16C852 will issue a receive ready interrupt when the
number of characters in the receive FIFO reaches the selected trigger level.
Refer to
Transmit trigger level in 32-byte FIFO mode
These bits are used to set the trigger level for the transmit FIFO interrupt and
flow control. The SC16C852 will issue a transmit empty interrupt when the
number of characters in FIFO drops below the selected trigger level. Refer to
Table
DMA mode select.
Transmit operation in mode ‘0’: When the SC16C852 is in the non-FIFO
mode (FIFOs disabled; FCR[0] = logic 0) or in the FIFO mode (FIFOs
enabled; FCR[0] = logic 1; FCR[3] = logic 0), and when there are no
characters in the transmit FIFO, the TXRDYA/TXRDYB pin will be a logic 0.
Once active, the TXRDYA/TXRDYB pin will go to a logic 1 after the first
character is loaded into the transmit holding register.
Receive operation in mode ‘0’: When the SC16C852 is in non-FIFO mode,
or in the FIFO mode (FCR[0] = logic 1; FCR[3] = logic 0) and there is at least
one character in the receive FIFO, the RXRDYA/RXRDYB pin will be a
logic 0. Once active, the RXRDYA/RXRDYB pin will go to a logic 1 when
there are no more characters in the receiver.
logic 0 = set DMA mode ‘0’ (normal default condition)
logic 1 = set DMA mode ‘1’
Rev. 01 — 31 August 2009
14.
Dual UART with 128-byte FIFOs and IrDA encoder/decoder
Table
13.
[1]
[2]
.
.
SC16C852
© NXP B.V. 2009. All rights reserved.
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