IBM Personal System/2 60 User Manual

g - Function
Parity Check
Channel Check
Timer 2 Output
Toggle with Each Refresh Request
Enable Channel Check
Enable Parity Check
Speaker Data Enable
Timer 2 Gate to Speaker
Figure 3-22. System Control Port B (Read)
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Bit7 Setting this bit to 1 during a write operation, resets IRQ 0.
When this port is read and this bit is set to 1, a parity
check has occurred.
Bit 6 When this port is read and this bit is set to 1, a channel
check has occurred.
BIt5 When this port is read, this bit indicates the condition of
the timer/counter 2 ‘output’ signal.
Bit 4 When this port is being read, this bit toggles for each
refresh request.
BIt3 Setting this bit to 0 enables channel check. It is set to 1
during a power-on reset.
Bit 2 Setting this bit to 0 enables parity checking. This bit is set
to 1 during a power-on reset.
Bit 1 Setting this bit to 1 enables speaker data. This bit is set to
0 during a power-on reset.
BitoO Setting this bit to 1 enables the timer 2 gate.
System Control Port A (Hex 0092)
Bit Function
7,6 Fixed Disk Activity Light
Reserved
Watchdog Timer Status
Security Lock Latch
Reserved
Alternate Gate A20
Alternate Hot Reset
Figure 3-23. System Control Port A (Hex 0092)
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Model 60 System Board — October 1990 3-21

IBM Personal System/2 60 Specifications

General

Brand	IBM
Model	Personal System/2 60
Category	Desktop
Language	English