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Type 2 Serial Port Controller
The Model 50 does not support FIFO mode operations even if a Type
2 serial controller is installed. Do not enable FIFO operations if the
modellsubmodel byte is hex FC/04.
The serial controller on some Type 2 system boards does not respond
the same as other Personal System/2 products. After the initial
transmitter-holding-register-empty interrupt, rewriting bit 1 of the
Interrupt Enable register as a 1 will not reissue an interrupt. The
interrupt is generated only when the Transmitter Holding register
becomes empty.
Hardware Compatibility
The Model 50 maintains many of the interfaces used by the IBM
Personal Computer AT. In most cases, command and status
organization of these interfaces is maintained.
The functional interfaces for the Personal System/2 products are
compatible with the following interfaces:
• The Intel
2
8259 interrupt controllers (without edge triggering).
• The Intel 8253 timers driven from 1.193 MHz (timer 0 and 2 only).
• The Intel 8237 DMA controller-address/transfer counters, page
registers and status fields only. The Command and Request
registers are not supported. The rotate and mask functions are
not supported. The Mode register is partially supported.
• Generally compatible with the NS16450 serial communications
controller.
• The Intel 8088, 8086, and 80286 microprocessors.
• The Intel 8272 diskette drive controller.
• The Motorola
3
MC146818 Time of Day Clock command and status
(CMOS reorganized).
• The Intel 8042 keyboard port at address hex 0060.
2
Intel is a trademark of the Intel Corporation.
3
Motorola Is a trademark of Motorola, Inc.
Model 50 System Board
3-29
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