MC68HC16Z1 Datasheet, PDF (395/500 Pages) Freescale Semiconductor, Inc – M68HC16Z Series

Freescale Semiconductor, Inc.
SPACE[1:0] — Address Space Select
Use this option field to select an address space for chip-select assertion or to configure
a chip-select as an interrupt acknowledge strobe for an external device. The CPU16
normally operates in supervisor mode only, but interrupt acknowledge cycles take
place in CPU space. Table D-17 shows address space bit encodings.
Table D-17 Address Space Bit Encodings
SPACE[1:0]
00
01
10
11
Address Space
CPU Space
User Space
Supervisor Space
Supervisor/User Space
IPL[2:0] — Interrupt Priority Level
When SPACE[1:0] is set for CPU space (%00), chip-select logic can be used as an
interrupt acknowledge strobe for an external device. During an interrupt acknowledge
cycle, the interrupt priority level is driven on address lines ADDR[3:1] and is then com-
pared to the value in IPL[2:0]. If the values match, an interrupt acknowledge strobe will
be generated on the particular chip-select pin, provided other option register condi-
tions are met. Table D-18 shows IPL[2:0] field encoding.
Table D-18 Interrupt Priority Level Field Encoding
IPL[2:0]
Interrupt Priority Level
000
Any Level¹
001
1
010
2
011
3
100
4
101
5
110
6
111
7
NOTES:
1. Any level means that chip-select is assert-
ed regardless of the level of the interrupt
acknowledge cycle.
AVEC — Autovector Enable
This field selects one of two methods of acquiring an interrupt vector during an inter-
rupt acknowledge cycle. This field is not applicable when SPACE[1:0] = %00.
0 = External interrupt vector enabled
1 = Autovector enabled
If the chip select is configured to trigger on an interrupt acknowledge cycle
(SPACE[1:0] = %00) and the AVEC field is set to one, the chip-select automatically
generates AVEC and completes the interrupt acknowledge cycle. Otherwise, the vec-
tor must be supplied by the requesting external device to complete the IACK read
cycle.
M68HC16 Z SERIES
USER’S MANUAL
REGISTER SUMMARY
For More Information On This Product,
Go to: www.freescale.com
D-21