SB16C1058PCI_Data Sheet_EN

SB16C1058PCI
PCI Target Interface Controller
with Octal-UART
JULY 2013 REV 1.04
40
■
If Xoff1 + Xoff2 character arrives during XOFF status, status is changed to XON by
Xoff1 and changed to XOFF again by Xoff2.
When Software flow control function and Special character function is enabled,
descriptions are as follows.
■
■
■
■
If Xoff1 character is used as Software flow control character, character in Xoff2
Register is recognized as Special character.
If Xoff2 character is used as Software flow control character, it is not recognized as
Special character but as Xoff character because both are same.
If Xoff1, Xoff2 character is sequential and Xoff1 + Xoff2 character is used as
Software flow control character, it is not recognized as Special character but as Xoff2
character because both are same.
If Xoff1 + Xoff2 character is used as Software flow control character and Xoff2
character which does not follow after Xoff1 character arrives, it is not recognized as
Xoff2 character but as Special character even though both are same.
12.3.3 Xon Any Function
While RX Software flow control function is enabled, data in TX FIFO are transmitted when
received Xon character and transmission is suspended when Xoff character is received.
This status is called ‘XOFF status’. Transmission is re-started when status changes to
‘XON status’ by incoming Xon character or Xon Any function that changes status when
any data arrives. Xon Any function is enabled if MCR[5] is set to 1b. While it is enabled,
XOFF status changes to XON status though Xoff character arrives.
Details about it are described in 12.3.2 Receive Software Flow Control.
12.3.4 Xoff Re-transmit Function
While TX Software flow control function is active, Xoff character is transmitted when the
amount of data in RX FIFO exceeds the value of FUR. Though it received Xoff character,
external UART may not recognize this character for some reason and continue to transmit
data. Under TX Software flow control, because Xoff character had been transmitted once
before, it is not transmitted again though more data arrive. In this situation, overflow may
occur in RX FIFO. Conventional UARTs can not deal this situation but SB16C1050 does
with Xoff Re-transmit function.
Xoff Re-transmit function transmits Xoff character again when more data arrives from
external UART though it transmitted Xoff character before. By this function the external
UART can recognize Xoff character and stop transmitting data though it didn’t recognize
the Xoff character before.
There are four Xoff Re-transmitting settings by XRCR[1:0]. Xoff character can be re-
transmitted when every 1, 4, 8 or 16 data arrives in XOFF status.
If XRCR[1:0] is 00b, Xoff character is re-transmitted whenever 1 more data arrives in
XOFF status. If XRCR[1:0] is ‘01’, Xoff character is re-transmitted whenever 4 more data
arrives in XOFF status.