參數(shù)資料
型號: CMQ82C55AZ96
廠商: INTERSIL CORP
元件分類: 微控制器/微處理器
英文描述: CMOS Programmable Peripheral Interface
中文描述: 24 I/O, PIA-GENERAL PURPOSE, PQFP44
封裝: ROHS COMPLIANT, PLASTIC, MS-022AB, MQFP-44
文件頁數(shù): 14/24頁
文件大小: 502K
代理商: CMQ82C55AZ96
14
FN6140.1
June 28, 2005
Special Mode Combination Considerations
There are several combinations of modes possible. For any
combination, some or all of Port C lines are used for control
or status. The remaining bits are either inputs or outputs as
defined by a “Set Mode” command.
During a read of Port C, the state of all the Port C lines,
except the ACK and STB lines, will be placed on the data
bus. In place of the ACK and STB line states, flag status will
appear on the data bus in the PC2, PC4, and PC6 bit
positions as illustrated by Figure 17.
Through a “Write Port C” command, only the Port C pins
programmed as outputs in a Mode 0 group can be written.
No other pins can be affected by a “Write Port C” command,
nor can the interrupt enable flags be accessed. To write to
any Port C output programmed as an output in Mode 1
group or to change an interrupt enable flag, the “Set/Reset
Port C Bit” command must be used.
With a “Set/Reset Port C Bit” command, any Port C line
programmed as an output (including IBF and OBF) can be
written, or an interrupt enable flag can be either set or reset.
Port C lines programmed as inputs, including ACK and STB
lines, associated with Port C are not affected by a “Set/Reset
Port C Bit” command. Writing to the corresponding Port C bit
positions of the ACK and STB lines with the “Set Reset Port
C Bit” command will affect the Group A and Group B
interrupt enable flags, as illustrated in Figure 17.
Current Drive Capability
Any output on Port A, B or C can sink or source 2.5mA. This
feature allows the 82C55A to directly drive Darlington type
drivers and high-voltage displays that require such sink or
source current.
Reading Port C Status
(Figures 15 and 16)
In Mode 0, Port C transfers data to or from the peripheral
device. When the 82C55A is programmed to function in
Modes 1 or 2, Port C generates or accepts “hand shaking”
signals with the peripheral device. Reading the contents of
Port C allows the programmer to test or verify the “status” of
each peripheral device and change the program flow
accordingly.
There is not a special instruction to read the status
information from Port C. A normal read operation of Port C is
executed to perform this function.
Applications of the 82C55A
The 82C55A is a very powerful tool for interfacing peripheral
equipment to the microcomputer system. It represents the
optimum use of available pins and is flexible enough to
interface almost any I/O device without the need for
additional external logic.
Each peripheral device in a microcomputer system usually
has a “service routine” associated with it. The routine
manages the software interface between the device and the
CPU. The functional definition of the 82C55A is programmed
by the I/O service routine and becomes an extension of the
system software. By examining the I/O devices interface
characteristics for both data transfer and timing, and
matching this information to the examples and tables in the
detailed operational description, a control word can easily be
developed to initialize the 82C55A to exactly “fit” the
application. Figures 18 through 24 present a few examples
of typical applications of the 82C55A.
INPUT CONFIGURATION
D5
D4
D7
D6
D3
D2
D1
D0
I/O
I/O
IBFA
INTEA INTRA INTEB
IBFB
INTRB
OUTPUT CONFIGURATION
D5
D4
D7
D6
D3
D2
D1
D0
OBFA
INTEA
I/O
I/O
INTRA INTEB
OBFB INTRB
FIGURE 15. MODE 1 STATUS WORD FORMAT
D7
D6
D5
D4
D3
D2
D1
D0
OBFA
INTE1
IBFA
INTE2 INTRA
X
X
X
(Defined by Mode 0 or Mode 1 Selection)
FIGURE 16. MODE 2 STATUS WORD FORMAT
GROUP A
GROUP B
GROUP A
GROUP B
GROUP A
GROUP B
INTERRUPT
ENABLE FLAG
POSITION
ALTERNATE PORT C
PIN SIGNAL (MODE)
INTE B
PC2
ACKB (Output Mode 1)
or STBB (Input Mode 1)
INTE A2
PC4
STBA (Input Mode 1 or Mode 2)
INTE A1
PC6
ACKA (Output Mode 1 or Mode 2)
FIGURE 17. INTERRUPT ENABLE FLAGS IN MODES 1 AND 2
MS82C55A, MQ82C55A
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