MCS9845 MosChip Semiconductor, MCS9845 Datasheet - Page 22

• Manufacturer Part Number: MCS9845
• Description: PCI Dual UART
• Manufacturer: MosChip Semiconductor

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MCS9845
PCI Dual UART with ISA Bridge
When the transmitter FIFO and THRE interrupt are
enabled (FCR-0=1, IER-1=1), transmit interrupts
occur as follows:
The occurrence of the Transmitter Holding Register
Empty interrupt is delayed one character time minus
the last stop bit time when there have not been at least
two Bytes in the transmitter FIFO at the same time
since the last time the transmitter FIFO was empty. It
is cleared as soon as the Transmitter Holding Register
is written to (1 to 16 characters may be written to the
transmit FIFO while servicing this interrupt) or the IIR
is read. The fi rst transmitter interrupt after changing
the FCR is immediate if it is enabled.
The Transmitter Empty indicator is delayed one
character time when there has not been at least two
Bytes in the transmitter FIFO at the same time since
the last time that TEMT=1. TEMT is set after the stop
bit has been completely shifted out.
The Transmitter FIFO Empty indicator is not delayed,
it is reported as soon as the condition occurs.
Page 22
Rev.
2.5