PCI_PCIe User Guide_RevA.pdf - Symmetricom

1.4. Device Registers
page 43 for more information on the format and use of this register.
MASK Register (0x18)
The TFM supports the seven interrupt sources listed in the following table. Each interrupt source can
be individually masked on or off using the MASK register (0x18). Each interrupt source sets a corresponding
bit in the INTSTAT register (0x1C) when the interrupt occurs.
Bits 0-6 in the MASK register correspond to interrupt sources zero through six listed in the following
table. An interrupt source is enabled (to generate a PCI interrupt) by writing a value of one to the corresponding
MASK bit. Writing a zero to the interrupt MASK bit disables that interrupt source.
INTSTAT Register (0x1C)
The INTSTAT register has the same structure as the MASK register listed in the following table. Each
interrupt source sets its corresponding bit in this register when it occurs. The INTSTAT register bits
get set regardless of the state of the MASK bits. INTSTAT bits are cleared by writing to the INTSTAT
register with the corresponding bit(s) set. For example, to clear INTSTAT bit zero, write 0x01 to the
INTSTAT register. To clear all INTSTAT bits simultaneously, write 0x7F to the INTSTAT register.
The corresponding INSTAT bit MUST be cleared in order to enable the next interrupt occurrence.
A PCI interrupt is generated anytime one or more INTSTAT bits [0 through 6] are set and the corresponding
bit(s) are set in the MASK register and interrupts have been enabled (started).
INTSTAT Register
Bit
Function
0 Event Input has occurred
1 Periodic/DDS Output has occurred
2 Strobe (time coincidence) has occurred
3 1 PPS output has occurred
4 GPS Data Packet is available (bc637 models only)
5 Signal transition on Event2 Input has occurred
6 Signal transition on Event3 Input has occurred
7-31 Reserved
Note: Register contents are undefined at reset.
MINSTRB (0x20) – MAJSTRB (0x24) Registers
These registers hold the programmed Time Coincidence Strobe time. The contents of these registers
depend on the time format selected. The Strobe time is programmable from hours through microseconds
in the decimal time format. When the time format is set to binary, only the 22 least sig-
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