CDP1877 Datasheet, PDF (1/10 Pages) Intersil Corporation – Programmable Interrupt Controller (PIC)

CDP1877,
CDP1877C
March 1997
Programmable Interrupt Controller (PIC)
Features
• Compatible with CDP1800 Series
• Programmable Long Branch Vector Address and
Vector Interval
• 8 Levels of Interrupt Per Chip
• Easily Expandable
• Latched Interrupt Requests
• Hard Wired Interrupt Priorities
• Memory Mapped
• Multiple Chip Select Inputs to Minimize Address
Space Requirements
Ordering Information
TEMP.
PACKAGE RANGE
5V
PKG.
10V
NO.
PDIP
-40^oC to CDP1877CE CDP1877E E28.6
+85^oC
Description
The CDP1877 and CDP1877C are programmable 8-level interrupt control-
lers designed for use in CDP1800 series microprocessor systems. They
provide added versatility by extending the number of permissible interrupts
from 1 to N in increments of 8.
When a high to low transition occurs on any of the PIC interrupt lines (IR0 to
IR7), it will be latched and, unless the request is masked, it will cause the
INTERRUPT line on the PIC and consequently the INTERRUPT input on
the CPU to go low.
The CPU accesses the PIC by having interrupt vector register R(1) loaded
with the memory address of the PIC. After the interrupt S3 cycle, this regis-
ter value will appear at the CPU address bus, causing the CPU to fetch an
instruction from the PIC. This fetch cycle clears the interrupt request latch
bit to accept a new high-to-low transition, and also causes the PIC to issue a
long branch instruction (CO) followed by the preprogrammed vector address
written into the PIC’s address registers, causing the CPU to branch to the
address corresponding to the highest priority active interrupt request.
If no other unmasked interrupts are pending, the INTERRUPT output of the
PIC will return high. When an interrupt is requested on a masked interrupt
line, it will be latched but it will not cause the PIC INTERRUPT output to go
low. All pending interrupts, masked and unmasked, will be indicated by a “1”
in the corresponding bit of the status register. Reading of the status register
will clear all pending interrupt request latches.
Several PICs can be cascaded together by connecting the INTERRUPT out-
put of one chip to the CASCADE input of another. Each cascaded PIC pro-
vides 8 additional interrupt levels to the system. The number of units
cascadable depends on the amount of memory space and the extent of the
address decoding in the system.
Interrupts are prioritized in descending order; IR7 has the highest and IR0
has the lowest priority.
The CDP1877 and CDP1877C are functionally identical. They differ in that
the CDP1877 has a recommended operating voltage range of 4V to 10.5V,
and the CDP1877C has a recommended operating voltage range of 4V to
6.5V.
Pinout
CDP1877, CDP1877C (PDIP)
TOP VIEW
CASCADE 1
IR7 2
IR6 3
IR5 4
IR4 5
IR3 6
IR2 7
IR1 8
IR0 9
TPA 10
TPB 11
MWR 12
MRD 13
V_SS 14
28 V_DD
27 BUS 7
26 BUS 6
25 BUS 5
24 BUS 4
23 BUS 3
22 BUS 2
21 BUS 1
20 BUS 0
19 CS/Ax
18 CS/Ay
17 CS
16 CS
15 INT
Programming Model
PROGRAMMABLE INTERRUPT CONTROLLER (PIC)
BUS 7
A15 A14
BUS 7
B7
B6
BUS 7
M7
M6
BUS 7
S7
S6
BUS 7
P7
P6
PAGE REGISTER
A13
A12
A11
A10
CONTROL REGISTER
B5
B4
B3
B2
MASK REGISTER
M5
M4
M3
M2
STATUS REGISTER
S5
S4
S3
S2
POLLING REGISTER
P5
P4
P3
P2
BUS 0
WRITE
A9
A8 ^ONLY
BUS 0
WRITE
B1
B0 ^ONLY
BUS 0
WRITE
M1
M0 ^ONLY
BUS 0
READ
S1
S0 ^ONLY
BUS 0
READ
P1
P0 ^ONLY
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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