Test if receive character available or loop if false> Read status (test for errors) If Error Post status Issue Reset Error command Increment "New Command Register" Exit Else Transfer Characters Issue Receiver Ack command Increment "New Command Regi ster" Exit Transfer Characters: While (Input Pointer) > (Output Pointer) Do { TTYlnputRoutine «BufferAddress)+(OutputPointer»; (OutputPointer) (OutputPointer)+l; If (OutputPointer) = (BufferLength) Then (0 u t put Po in t e r ) QJ; } Modem status Operation Synchronous modern operation is available on Port 3 of the main controller unit rear panel. Asynchronous modern operation may be setup on Ports I through Port 5.
Refer to the Channel Command Register described in the Register Definition section. Test if last command still pending or loop if true> Test if modern status changed or loop if fal se> Read status (test for errors) Issue Reset Modern Interrupt command Increment "New Command Register" Exit Execute from XLA Bus REGISTER DEFINITIONS The following provides register definitions for the Z-8QJA I/O controll er. Initialization Register The Initialization Register is a 24-bit register residing at location lFFFC (hex). It contains the address of the system and channel. 5-38