mcs7715 MosChip, mcs7715 Datasheet - Page 17

• Manufacturer Part Number: mcs7715
• Description: Usb 1.1 To Single Uart And Printer Port
• Manufacturer: MosChip

Rev. 1.6
Interrupt Status Register:
The source of the highest priority interrupt pending is indicated by the contents of the Interrupt Status Register
(ISR). There are five sources of interrupts, and four levels of priority (1 is the highest) as tabulated below.
Register:
Description:
Offset:
Permissions:
Interrupt Descriptions:
Level1: Receiver Status Error
Normal Mode: This interrupt is active whenever any of the LSR[1], LSR[2], LSR[3] or LSR[4] are set. These
flags are cleared following a read of the LSR. The interrupt is masked with IER[2].
Level 2a: Receiver Data Available
The interrupt is active whenever the receiver FIFO level is above the interrupt trigger level.
Level 2b: Receiver Time-Out
A receiver time out event, (which may cause an interrupt) will occur when all of the following conditions are
true:
Reading the first data item in RHR clears this interrupt.
Level 3: Transmitter Empty
This interrupt is set when the transmit FIFO level falls below the trigger level. It is cleared on the ISR read to
Level-3 interrupt or by writing more data to the THR so that the trigger level is exceeded.
Level 4: Modem Change
This interrupt is set by the modem change flag (MSR[0], MSR[1], MSR[2] or MSR[3]) becoming active due to
changes in the input modem lines. This interrupt is cleared following the read of the MSR register.
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•
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The UART is in the FIFO Mode.
There is data in the RHR
There has been no read of the RHR for a period of time greater than the timeout period. The time-
out period of time is greater than the time out period. The time out period is four times the character
period (including start & stop bits) measured from the centre of the first stop bit of the first data item
received.
Bit[7]
Enabled
FIFOs
Level
ISR
Interrupt Status Register
010
Read
2a
2b
1
3
4
-
Note: ISR[0] indicates whether any interrupt is pending
Bit[6]
or address bit detected in 9-bit mode
Bit[5]
(Enhanced Mode)
Receiver Data Available
Transmitter THR Empty
Modem Status Change
Interrupt Priority
Receiver Status Error
No interrupt pending
Receiver Time Out
Interrupt Source
Bit[4]
USB 1.1 to Single UART and Printer Port
Bit[3]
Interrupt Priority
(All Modes)
6’b000001
6’b000110
6’b000100
6’b001100
6’b000010
6’b000000
ISR[5:0]
Bit[2]
MCS7715
Bit[1]
Interrupt
Pending
Bit[0]
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