![](http://datasheet.mmic.net.cn/140000/SPAKXC16Z1MFC16_datasheet_5015162/SPAKXC16Z1MFC16_69.png)
MC68HC16Z1
MOTOROLA
MC68HC16Z1TS/D
69
knowledge cycle is transferred to the external bus, an external device must decode the mask value and
respond with a vector number, then generate bus cycle termination signals. If the device does not re-
spond in time, a spurious interrupt exception is taken.
The periodic interrupt timer (PIT) in the SIM can generate internal interrupt requests of specific priority
at predetermined intervals. By hardware convention, PIT interrupts are serviced before external inter-
3.7.2 Interrupt Processing Summary
A summary of the interrupt processing sequence follows. When the sequence begins, a valid interrupt
service request has been detected and is pending.
The CPU finishes higher priority exception processing or reaches an instruction boundary.
Processor state is stacked, then the CCR PK extension field is cleared.
The interrupt acknowledge cycle begins:
— FC[2:0] are driven to %111 (CPU space) encoding.
— The address bus is driven as follows. ADDR[23:20] = %1111; ADDR[19:16] = %1111, which
indicates that the cycle is an interrupt acknowledge CPU space cycle; ADDR[15:4] =
%11111111111; ADDR[3:1] = the priority of the interrupt request being acknowledged; and
ADDR0 = %1.
— Request priority is latched into the CCR IP field from the address bus.
Modules or external peripherals that have requested interrupt service decode the priority value in
ADDR[3:1]. If request priority is the same as the priority value in the address, IARB contention
takes place. When there is no contention, the spurious interrupt monitor asserts, and a spurious
interrupt exception is processed.
After arbitration, the interrupt acknowledge cycle can be completed in one of three ways:
— The dominant interrupt source supplies a vector number and signals appropriate to the access.
The CPU16 acquires the vector number.
— The signal is asserted (the signal can be asserted by the dominant interrupt source or the pin
can be tied low), and the CPU16 generates an autovector number corresponding to interrupt
priority.
— The bus monitor asserts and the CPU16 generates the spurious interrupt vector number.
The vector number is converted to a vector address.
The content of the vector address is loaded into the PC, and the processor transfers control to the
exception handler routine.
3.8 Factory Test Block
The test submodule supports scan-based testing of the various MCU modules. It is integrated into the
SIM to support production test.
3.8.1 Test Registers
Test submodule registers are intended for Motorola use. Register names and addresses are provided
to indicate that these addresses are occupied.
SIMTR — System Integration Test Register
$YFFA02
SIMTRE — System Integration Test Register (E Clock)
$YFFA08
TSTMSRA — Master Shift Register A
$YFFA30
TSTMSRB — Master Shift Register B
$YFFA32
TSTSC — Test Module Shift Count
$YFFA34
TSTRC — Test Module Repetition Count
$YFFA36
CREG — Test Submodule Control Register
$YFFA38
DREG — Distributed Register
$YFFA3A