
á
PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
121
local
μ
C/
μ
P must do within the user supplied “UNI” in-
terrupt service routine, is to perform a read of the
UNI Interrupt Status Register (Address = 05h) within
the XRT7245 UNI device. The bit format of the UNI
Interrupt Status Register is presented below.
The UNI Interrupt Status Register presents the “inter-
rupt request” status of each functional block within the
chip. The purpose of the UNI Interrupt Status Register
is to help the local μP/μC identify which functional
block(s) has requested the interrupt. Whichever bit(s)
are asserted in this register, identifies which block(s)
have experienced an “interrupt-generating” condition
as presented in Table 6. Once the local μP/μC has
read this register, it can determine which “branch”
within the interrupt service routine that it must follow
in order to properly service this interrupt.
The UNI further supports the Functional Block hierar-
chy by providing the UNI Interrupt Enable Register (Ad-
dress = 04h). The bit format of this register is identical
to that for the UNI Interrupt Status register, and is
presented below for the sake of completeness.
The UNI Interrupt Enable Register allows the user to
individually enable or disable the interrupt requesting
capability of the functional blocks within the UNI. If a
particular bit field within this register contains the value
“0”, then the corresponding functional block has been
disabled from generating any interrupt requests.
Conversely, if that bit field contains the value “1”, then
the corresponding functional block has been enabled
for interrupt generation (e.g., those potential inter-
rupts, within the ‘enabled functional block’ that are
enabled at the source level, are now enabled). The
user should be aware of the fact that each functional
block within the UNI contains anywhere from 1 to 7
potential interrupt sources. Each of these lower level
interrupt sources contain their own set of interrupt
enable bits and interrupt status bits, existing in various
on-chip registers.
Interrupt Service Routine Branching: after reading
the UNI Interrupt Status Register
The contents of the UNI Interrupt Status Register
identify which of 8 functional blocks (within the UNI IC)
have requested interrupt service. The local
μ
P should
use this information in order to determine where, with-
in the Interrupt Service Routine, program control
should branch to. The following table can be viewed as
an “interrupt service routine” guide. It lists each of the
Functional Blocks that contain a bit-field in the UNI
Interrupt Status Register. Additionally, this table also
presents a list and addresses of corresponding on-
chip Registers that the Interrupt Service Routine
should branch to and read; based upon the Interrupt-
ing Functional Block.
UNI Interrupt Status Register: Address = 05h
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Rx DS3
Interrupt
Status
Rx PLCP
Int. Stat
Rx CP
Interrupt
Status
Rx UTOPIA
Int. Stat
Tx UTOPIA
Int. Stat
Tx CP
Interrupt
Status
Tx DS3
Interrupt
Status
One Sec
Interrupt
Status
RO
RO
RO
RO
RO
RO
RO
RUR
UNI Interrupt Enable Register: Address = 04h
B
IT
7
B
IT
6
B
IT
5
B
IT
4
B
IT
3
B
IT
2
B
IT
1
B
IT
0
Rx DS3
Interrupt
Status
Rx PLCP
Int. Status
Rx CP
Interrupt
Status
Rx UTOPIA
Int. Status
Tx UTOPIA
Int. Stat
Tx CP
Interrupt
Status
Tx DS3
Interrupt
Status
One Sec
Interrupt
Status
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W