MSM82C55A-2RS Datasheet, PDF (20/26 Pages) OKI electronic componets – CMOS PROGRAMMABLE PERIPHERAL INTERFACE

¡ Semiconductor
MSM82C55A-2RS/GS/VJS
5. Port C Status Read
When port C is used for the control signal, that is, in either mode 1 or mode 2, each control
signal and bus status signal can be read out by reading the content of port C.
The status read out is as follows:
Group A Group B
1 ^{Mode 1}
Input
2 ^{Mode 1}
Output
3 Mode 0
4 Mode 0
5 ^{Mode 1}
Input
6 ^{Mode 1}
Input
7
Mode 1
Output
8 ^{Mode 1}
Output
9 Mode 2
10 ^{Mode 2}
11 Mode 2
Mode 0
Mode 0
Mode 1
Input
Mode 1
Output
Mode 1
Input
Mode 1
Output
Mode 1
Input
Mode 1
Output
Mode 0
Mode 1
Input
Mode 1
Output
D₇
I/O
OBF_A
I/O
I/O
I/O
I/O
OBF_A
OBF_A
OBF_A
OBF_A
OBF_A
D₆
I/O
INTE_A
I/O
I/O
I/O
I/O
INTE_A
INTE_A
INTE₁
INTE₁
INTE₁
Status Read on the Data Bus
D₅
D₄
D₃
D₂
D₁
D₀
IBF_A INTE_A INTR_A
I/O
I/O
I/O
I/O
I/O
INTR_A
I/O
I/O
I/O
I/O
I/O
I/O
INTE_B IBF_B INTR_B
I/O
I/O
I/O
INTE_B OBF_B INTR_B
IBF_A INTEA INTRA INTEB IBF_B INTR_B
IBF_A INTEA INTRA INTEB OBF_B INTR_B
I/O
I/O
INTR_A INTE_B IBF_B INTR_B
I/O
I/O
INTR_A INTE_B OBF_B INTR_B
IBF_A INTE2 INTRA
I/O
I/O
I/O
IBF_A INTE2 INTRA INTEB IBF_B INTR_B
IBF_A INTE2 INTRA INTEB OBF_B INTR_B
6. Reset of MSM82C55A-2
Be sure to keep the RESET signal at power ON in the high level at least for 50 ms.
Subsequently, it becomes the input mode at a high level pulse above 500 ns.
Note: Comparison of MSM82C55A-5 and MSM82C55A-2
MSM82C55A-5
After a write command is executed to the command register, the internal latch is cleared in
PORTA PORTC. For instance, 00H is output at the beginning of a write command when
the output port is assigned. However, if PORTB is not cleared at this time, PORTB is
unstable. In other words, PORTB only outputs ineffective data (unstable value according
to the device) during the period from after a write command is executed till the first data
is written to PORTB.
MSM82C55A-2
After a write command is executed to the command register, the internal latch is cleared in
All Ports (PORTA, PORTB, PORTC). 00H is output at the beginning of a write command
when the output port is assigned.
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