M68HC16 Z SERIES
GENERAL-PURPOSE TIMER
USER’S MANUAL
11-5
For each bit in TFLG1 and TFLG2 there is a corresponding bit in TMSK1 and TMSK2
in the same bit position. If a mask bit is set and an associated event occurs, a hard-
ware interrupt request is generated.
In order to re-enable a status flag after an event occurs, the status flags must be
cleared. Status registers are cleared in a particular sequence. The register must first
be read for set flags, then zeros must be written to the flags that are to be cleared. If
a new event occurs between the time that the register is read and the time that it is
written, the associated flag is not cleared.
11.4.2 GPT Interrupts
The GPT has 11 internal sources that can cause it to request interrupt service (refer
to
). Setting bits in TMSK1 and TMSK2 enables specific interrupt sources.
TMSK1 and TMSK2 are 8-bit registers that can be addressed individually or as one
16-bit register. The registers are initialized to zero at reset. For each bit in TMSK1 and
TMSK2 there is a corresponding bit in TFLG1 and TFLG2 in the same bit position.
TMSK2 also controls the operation of the timer prescaler. Refer to
for
more information.
The value of the interrupt priority level (IPL[2:0]) field in the interrupt control register
(ICR) determines the priority of GPT interrupt requests. IPL[2:0] values correspond to
MCU interrupt request signals IRQ[7:1]. IRQ7 is the highest priority interrupt request
signal; IRQ1 is the lowest-priority signal. A value of %111 causes IRQ7 to be asserted
when a GPT interrupt request is made; lower field values cause corresponding lower-
priority interrupt request signals to be asserted. Setting field value to %000 disables
interrupts.
Table 11-1 GPT Status Flags
Flag
Mnemonic
Register
Assignment
Source
IC1F
TFLG1
Input capture 1
IC2F
TFLG1
Input capture 2
IC3F
TFLG1
Input capture 3
OC1F
TFLG1
Output compare 1
OC2F
TFLG1
Output compare 2
OC3F
TFLG1
Output compare 3
OC4F
TFLG1
Output compare 4
I4/O5F
TFLG1
Input capture 4/output compare 5
TOF
TFLG2
Timer overflow
PAOVF
TFLG2
Pulse accumulator overflow
PAIF
TFLG2
Pulse accumulator input
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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