Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
To provide for data transfer at a maximum rate between a host system and a PC running a terminal emulator, alphanumeric replacement (ANR) hardware is allowed to share the PC direct-memory access (DMA) channels between the ANR card and the disk control cards. When this was done, a method to interlock the host computer and the ANR hardware was created so that no data was lost during an upload or download operation. The ANR interface in the host computer had a provision for a busy signal, but it was only recognized at idle poll time or during the first read poll of a read/write sequence to the ANR card. To interlock the PC microprogram to the host computer, a Busy Pending Latch was added to the ANR card. This gives the PC complete control of setting the busy signal to the host controller.