SB16C1058-TQFP128 IK Semicon Co., Ltd, SB16C1058-TQFP128 Datasheet - Page 18

• Manufacturer Part Number: SB16C1058-TQFP128
• Description: Octal-uart Controller With 256-byte Fifo
• Manufacturer: IK Semicon Co., Ltd

IN16C1058
OCTAL UART WITH 256-BYTE FIFO
JUNE 2009
Figure 4:
18
RCR[7:0]
nRTS
nIOR
RXD
NRTS Functional Timing
REV 1.0
START
6.4.2 Auto-CTS
FUR + 0
DATA BYTE n-1
changed to ‘1’ until the amount in RX FIFO exceeds the value set in FUR. But if NRTS is
‘1’ now, NRTS 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 NRTS
is ‘0’ or ‘1’ by FSR[5]. If FSR[5] is ‘0’, NRTS 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 NRTS 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 NRTS 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, NRTS is asserted for external UART to transmit new data.
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
NCTS by FSR[1]. If ‘0’, NCTS is ‘0’ and it means external UART can accept new data,
If ’1’, NCTS 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 NCTS is changed from ‘0’ to ‘1’, and it is shown on ISR[5:0]. Interrupts
STOP
FUR + 1
DATA BYTE 1
START
DATA BYTE 2
FUR -0
DATA BYTE n
FUR - 1
STOP
FUR - 0
DATA BYTE n
FLR + 1
FLR + 0
START