SB16C1058_Data Sheet_EN

SB16C1058

OCTAL UART WITH 256-BYTE FIFO

JULY 2013 REV 1.04

‘1’ now, RTS# is not changed to ‘0’ until the amount in RX FIFO equals the value written

in FLR.

The value of FUR and FLR is determined by FIFO mode. If FCR[7:6] holds ‘00’, ’01’, ‘10’,

and ‘11’, FUR stores 8, 16, 56, and 60, respectively. And if FCR[5:4] holds ‘00’, ’01’, ‘10’,

and ‘11’, FLR stores 0, 8, 16, and 56, respectively in 64-byte FIFO. In 256-byte FIFO

mode, users can write FUR and FLR values as they want and use them. But the value of

FUR must be larger than that of FLR. While Auto-RTS is enabled, you can verify if RTS#

is ‘0’ or ‘1’ by FSR[5]. If FSR[5] is ‘0’, RTS# is ‘0’ and if ‘1’, NRTS is ‘1’, too.

When IER[6] is set to ‘1’ and NRTS is changed from ‘0’ to ‘1’ by Auto-RTS function,

interrupt occurs and it is displayed on ISR[5:0]. Interrupts by Auto-RTS function are

removed if MSR is read. NRTS is changed from ‘0’ to ‘1’ after the first STOP bit is

received. Figure 4 shows the NRTS timing chart while Auto-RTS is enabled.

In Figure 4, Data Byte n-1 is received and RTS# is deasserted when the amount of data

in RX FIFO is larger than the value written in FUR. UART completes transmitting new

data (DATA BYTE n) which has started being transmitted even though external UART

recognizes RTS# has been deasserted. After that, the device stops transmitting more

data. If CPU reads data of RX FIFO, the value of RCR decreases and then if that value

equals that of FLR, RTS# is asserted for external UART to transmit new data.

Figure 4: RTS# Functional Timing

6.4.2 Auto-CTS

Setting EFR[7] to ‘1’ enables Auto-RTS. If enabled, data in TX FIFO are determined to be

transmitted or suspended by the value of NCTS. If ‘0’, it means external UART can

receive new data and data in TX FIFO are transmitted through TXD pin. If ‘1’, it means

external UART can not accept more data and data in TX FIFO are not transmitted. But

data being transmitted by then complete transmission. These procedures are performed

irrespective of FIFO modes. While Auto-CTS is enabled, you can verify the input value of

CTS# by FSR[1]. If ‘0’, CTS# is ‘0’ and it means external UART can accept new data,

If ’1’, CTS# is ‘1’ and it means external UART can not accept more data and data in TX

FIFO are not being transmitted. If IER[7] is set to ‘1’, interrupt is generated by Auto-CTS

when the input of CTS# is changed from ‘0’ to ‘1’, and it is shown on ISR[5:0]. Interrupts

generated by Auto-CTS are removed if MSR is read.

START

IOR#

DATA BYTE n-1 STOP START DATA BYTE n STOP

DATA BYTE 1 DATA BYTE 2 DATA BYTE n

START

FUR + 0 FUR -0FUR + 1 FUR - 0FUR - 1 FLR + 1 FLR + 0

RXD

RTS#