Z8E520 Datasheet, PDF (24/43 Pages) Zilog, Inc. – 1.5 MBPS USB Device Controller

Z8E520/C520
1.5 MBPS USB Device Controller
Zilog
COMMUNICATION REGISTER DEFINITIONS (USB MODE) (Continued)
LOW PRIORITY INTR: This register contains the IRQ
source flags of a low-priority communications interrupt.
The ISR should check these bits to determine the cause of
the interrupt. The definition of these bits depends on the
EP Mode as specified in the USB CSR. Writing a 1 to their
position clears interrupt sources. Read/Write.
LOW PRIORITY MASK: This register contains mask bits
for the IRQ sources specified in the LOW PRIORITY INTR
register. A set bit indicates that the corresponding interrupt
source is unmasked.
Table 10 illustrates both Low Priority MASK and INTR con-
ditions according to EP Mode:
Table 10. Low Priority MASK and INTR Conditions
EP
MODE
000
001
010
011
100
101
110
111
Description
EP1 OFF, EP2 OFF
EP 2
EP 1
EP1 IN EP2 OFF
EP1 OUT, EP2 OFF
EP1 CONTROL
EP1 OUT, EP2 OUT
EP1 IN, EP1 OUT
EP1 OUT, EP1 IN
EP1 IN EP2 IN
OUT
NAK
SENT
OUT
NAK
SENT
OUT
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
IN
DONE
IN
DONE
IN
NAK
SENT
OUT
NAK
READY
IN
NAK
SENT
OUT
NAK
SENT
IN
NAK
SENT
OUT
NAK
SENT
IN
NAK
SENT
IN
DONE
OUT
PACKET
READY
IN
DONE
OUT
PACKET
READY
IN
DONE
OUT
PACKET
READY
IN
DONE
OUT
NAK
SENT
OUT
NAK
SENT
OUT
NAK
SENT
OUT
NAK
SENT
OUT
NAK
SENT
OUT
NACK
SENT
OUT
NAK
SENT
OUT
NACK
SENT
EP 0
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
OUT
PACKET
READY
IN
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
IN
NAK
SENT
IN
DONE
IN
DONE
IN
DONE
IN
DONE
IN
DONE
IN
DONE
IN
DONE
IN
DONE
IN DONE: The SIE received a valid IN token, sent the data
packet and received an ACK from the host. Setting this bit
by the SIE, clears IN PACKET READY and IN NAK SENT.
SIE may never write to the IN buffer.
IN NAK SENT: The SIE sent a NAK on an IN transmission
because IN PACKET READY was clear.
OUT PACKET READY: The SIE received a valid OUT
packet and placed the received data, if any, in the buffer,
thereby updating the OUT count register and sending an
ACK. Setting this bit by the SIE clears OUT SERVICED
and OUT NAK SENT. Firmware may never write to the
OUT buffer.
OUT NAK SENT: The SIE sent a NAK on an OUT trans-
action because OUT SERVICED was clear. If an OUT
packet was NAK’d, OUT DATA TOGGLE and the OUT
buffer must not be affected.
24
PRELIMINARY
DS97KEY2005