83Plus:Ports:08

Synopsis

Port Number: 08h

Function: Link Assist Enable

This port controls whether the hardware link assist is enabled.

Read Values

• Bit 1: 1 if link assist will generate an interrupt when a byte is received.(Link assist must be enabled)
• Bit 7: 1 if the link assist is disabled.

Write Values

• Bit 1: Set to generate an interrupt when link assist receives a byte.(Link assist must be enabled)
• Bit 7: 1 to disable the link assist.

Comments

This port only exists on the 83+ SE and the 84+.

Programs which directly control the link port should disable the hardware assist.

Interrupts

Link Assist hardware can generate an interrupt when a byte is recieved. To enable this write 01 to port 08. When a byte recieved and an interrupt is generated bit 0 of port 9 is set. Like all interrupts this one needs to be acknowledged, do this by reading the byte from port 0A.

Credits and Contributions

• Michael Vincent: Original documentation of the link assist