
A-16
SIGNALS REFERENCE
A.1.34. INTR (I)
The INTR signal is the Interrupt Request signal. The INTR input indicates that an external in-
terrupt has been generated. The interrupt is maskable using the IF bit in the EFLAGS register. If
the IF bit is set, the Pentium Pro processor vectors to the interrupt handler after the current in-
struction execution is completed. Upon recognizing the interrupt request, the Pentium Pro pro-
cessor issues a single Interrupt Acknowledge (INTA) bus transaction. INTR must remain active
until the INTA bus transaction to guarantee its recognition.
INTR is sampled on every rising BCLK edge. INTR is an asynchronous input but recognition
of INTR is guaranteed in a specific clock if it is asserted synchronously and meets the setup and
hold times. INTR must also be deasserted for a minimum of two clocks to guarantee its inactive
recognition. In FRC mode, INTR must be synchronous to BCLK. On power-up the LINT[1:0]
signals are used for power-on-configuration of clock ratios. Both these signals must be software
configured by programming the APIC register space to be used either as NMI/INTR or LINT[1:0]
in the BIOS. Because APIC is enabled after reset, LINT[1:0] is the default configuration.
A.1.35. LEN[1:0]# (I/O)
The LEN[1:0]# signals are data-length signals. They are transmitted using REQb[1:0]# signals
by the request initiator in the second clock of Request Phase. LEN[1:0]# define the length of the
data transfer requested by the request initiator as defined in Table A-8. The LEN[1:0]#, HITM#,
and RS[2:0]# signals together define the length of the actual data transfer.
A.1.36. LINT[1:0] (I)
The LINT[1:0] signals are the Execution Control group Local Interrupt signals. When APIC is
disabled, the LINT0 signal becomes INTR, a maskable interrupt request signal, and LINT1 be-
comes NMI, a non-maskable interrupt. INTR and NMI are backward compatible with the same
signals for the Pentium processor. Both signals are asynchronous inputs. In FRC mode,
LINT[1:0] must be synchronous to BCLK.
During active RESET#, the Pentium Pro processor continuously samples the A20M#, IGNNE#,
and LINT[1:0] values to determine the ratio of core-clock frequency to bus-clock frequency. Af-
ter the PLL-lock time, the core clock becomes stable and is locked to the external bus clock. On
the active-to-inactive transition of RESET#, the Pentium Pro processor freezes the frequency ra-
tio internally.
Table A-8. LEN[1:0]# Signals Data Transfer Lengths
LEN[1:0]#
Request Initiator’s Data Transfer Length
00
0-8 Bytes
01
16 Bytes
10
32 Bytes
11
Reserved
Содержание Pentium Pro Family
Страница 17: ...1 Component Introduction ...
Страница 26: ...2 Pentium Pro Processor Architecture Overview ...
Страница 27: ......
Страница 36: ...3 Bus Overview ...
Страница 62: ...4 Bus Protocol ...
Страница 105: ...5 Bus Transactions and Operations ...
Страница 126: ...6 Range Registers ...
Страница 131: ...7 Cache Protocol ...
Страница 135: ...8 Data Integrity ...
Страница 148: ...9 Configuration ...
Страница 161: ...10 Pentium Pro Processor Test Access Port TAP ...
Страница 172: ...11 Electrical Specifications ...
Страница 201: ...12 GTL Interface Specification ...
Страница 229: ...13 3 3V Tolerant Signal Quality Specifications ...
Страница 233: ...14 Thermal Specifications ...
Страница 239: ...15 Mechanical Specifications ...
Страница 241: ...15 2 MECHANICAL SPECIFICATIONS s Figure 15 1 Package Dimensions Bottom View ...
Страница 252: ...16 Tools ...
Страница 260: ...16 8 TOOLS Figure 16 4 Generic MP System Layout for Debug Port Connection ...
Страница 264: ...17 OverDrive Processor Socket Specification ...
Страница 290: ...A Signals Reference ...
Страница 320: ...Index ...
Страница 328: ......