
MC68331
USER’S MANUAL
REGISTER SUMMARY
MOTOROLA
D-5
D
FRZ[1:0] — FREEZE Response
FRZ1 is not used; FRZ0 encoding determines response to the IMB FREEZE signal.
0 = Ignore IMB FREEZE signal
1 = Freeze the current state of the GPT
STOPP — Stop Prescaler
0 =Normal operation
1 =Stop prescaler and pulse accumulator from incrementing. Ignore changes to in-
put pins.
INCP — Increment Prescaler
0 =Has no meaning
1 =If STOPP is asserted, increment prescaler once and clock input synchronizers
once.
SUPV — Supervisor/Unrestricted Data Space
0 =Registers with access controlled by the SUPV bit are accessible from either the
user or supervisor privilege level.
1 =Registers with access controlled by the SUPV bit are restricted to supervisor
access only.
Each module that generates interrupts must have an IARB value. IARB values are
used to arbitrate between interrupt requests of the same priority.
D.2.2 GPTMTR
— GPT Module Test Register (Reserved)
This address is currently unused and returns zeros when read. It is reserved for GPT
factory test.
$YFF902
D.2.3 ICR
— GPT Interrupt Configuration Register
$YFF904
ICR fields determine internal and external interrupt priority, and provide the upper nib-
ble of the interrupt vector number supplied to the CPU when an interrupt is acknowl-
edged.
IPA — Interrupt Priority Adjust
Specifies which of the 11 internal GPT interrupt sources is assigned highest priority.
IPL — Interrupt Priority Level
Specifies the priority level of GPT interrupt requests.
IVBA — Interrupt Vector Base Address
Contains the most significant nibble of interrupt vector numbers supplied by the GPT.
15
12
11
10
8
7
4
3
2
1
0
IPA
0
IPL
IVBA
0
0
0
0
RESET:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0