MPC555
/
MPC556
SYSTEM CONFIGURATION AND PROTECTION
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
6-31
initialization. The contents of the register may be written by the
mttbl
or the
mttbu
in-
structions, see
3.9.4 Time Base Facility (TB) — OEA
Refer to
3.8 PowerPC VEA Register Set — Time Base
and
for more information on reading and writing the TBU and TBL registers.
6.13.4.3 Time Base Reference Registers
Two reference registers (TBREF0 and TBREF1) are associated with the lower part of
the time base (TBL). Each is a 32-bit read/write register. Upon a match between the
contents of TBL and the reference register, a maskable interrupt is generated.
6.13.4.4 Time Base Control and Status Register
The TBSCR is 16-bit read/write register. It controls the TB, decrementer count enable,
and interrupt generation and is used for reporting the source of the interrupts. The reg-
ister can be read anytime. A status bit is cleared by writing a one to it. (Writing a zero
has no effect.) More than one bit can be cleared at a time.
TB
— Time Base (Reading)
SPR 268, 269
MSB
0
31 32
LSB
63
TBU
TBL
RESET: UNCHANGED
TB
— Time Base (Writing)
SPR 284, 285
MSB
0
31 32
LSB
63
TBU
TBL
RESET: UNCHANGED
TBREF0
— Time Base Reference Register 0
0x2F C204
MSB
0
LSB
31
TBREF0
RESET:
TBREF1
— Time Base Reference Register 1
0x2F C208
MSB
0
LSB
31
TBREF1
RESET:
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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