Usb Interrupt Status Registers - Renesas M16C Series User Manual

M30240 Group

3.2.2.5 USB Interrupt Status Registers

These registers are used to determine the condition that caused a USB function interrupt, and to indi-
cate a USB Reset, Suspend and Resume interrupt. When an interrupt request occurs, the correspond-
ing status flag is set to "1". To clear a status flag, the CPU writes a "1" to the bit to be cleared.
Because the USB Function Interrupt has multiple sources that can generate an interrupt, it is recommended that
the user first read the two status registers and store them in variables then write back the same value for clearing
all the existing interrupts that were pending when the status registers were read. This procedure prevents any
interrupt that occurs after the status registers are read from being cleared by the 'write-back' operation. The CPU
must read, then write both status registers, writing to status register 1 first and status register 2 second to guar-
antee proper operation.
"Read-modify-write' instructions, such as "BCLR' and 'BSET', should not be used to clear any of the interrupt sta-
tus bits in USBIS1 or USBIS2. Using these instructions could cause pending interrupts to be cleared without the
firmware's knowledge.
Figure 3.11 shows the structures of USB interrupt status register 1 and USB interrupt status register 2
USB Interrupt Status Register 1
b7 b6 b5 b4 b3
USB Interrupt Status Register 2
b7 b6 b5 b4 b3
O O
Figure 3.11: USB Interrupt Status Registers (USBIS1, USBIS2)
Rev.1.00 Sep 24, 2003 Page 298 of 360
b2 b1 b0
Symbol
O
USBIS1
Bit Symbol
USB Endpoint 0 Interrupt
INTST0
Status Flag
Reserved
USB Endpoint 1 IN
INTST2
Interrupt Status Flag
USB Endpoint 1 OUT
INTST3
Interrupt Status Flag
USB Endpoint 2 IN
INTST4
Interrupt Status Flag
USB Endpoint 2 OUT
INTST5
Interrupt Status Flag
USB Endpoint 3 IN
INTST6
Interrupt Status Flag
USB Endpoint 3 OUT
INTST7
Interrupt Status Flag
b2 b1 b0
Symbol
USBIS2
Bit Symbol
USB Endpoint 4 IN
INTST8
Interrupt Status Flag
USB Endpoint 4 OUT
INTST9
Interrupt Status Flag
Reserved
USB Overrun/Underrun
INTST12
Interrupt Status Flag
USB Reset
INTST13
Interrupt Status Flag
USB Resume Signaling
INTST14
Interrupt Status Flag
USB Suspend Signaling
INTST15
Interrupt Status Flag
Address When reset
0302 00
16 16
Bit Name Function
0: No Interrupt Request issued
1: Interrupt request issued
Must always be set to "0"
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
Address When reset
0303 00
16 16
Bit Name Function
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
Must always be set to "0"
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
0: No Interrupt Request issued
1: Interrupt request issued
Universal Serial Bus
.
R W
O O
O O
O O
O O
O O
O O
O O
O O
R W
O O
O O
O O
O O
O O
O O
O O