TNS-LAN-AT
Network card for TNS-Net 900 (TNS AT, TNS XT), uses P8274 and Z80.
Since 2n there is another variant of LAN-AT (V 00) with Z80, and then LAN-AT-WACE (MX 01), but both have instead of P8274 Z80 SIO, so they are more similar to the card. Unlike the mileage, they use Dram and are more complex.
TNS-AT/XT computers. Inserted into a free expansion slot, the computer becomes part of the TNS-LAN computer network, which also consists of TNS HC-16 PXT computers, or other TNS AT/XT computers.
Power supply:
+5 V / 550 ma
+12 V / 60 ma
-5 (-12) in / 10 ma
The data register is located at 360h, status register at 362H. Standard values are set for communication: IRQ2, -DRQ1, -DACK1 that can be changed.
The core of the board consists of a multiprotocol-coaches transmitter i8274 (2x serial channel) operating in the SDLC protocol. Only channel A. is used only A.
The time base consists of three IO1A, IO1B, IO1C and IO2 IO2 Hraps (74ALS193). The Memory of Prom Io7 (74S571) is used as the address decoder. The driver of the data signals is IO6 (74ALS245). IO9 (74ALS244) is designed to read the selected station number.
IO10, IO1, IO12B circuits create a transmitted signal, which is subsequently amplified by the IO13 circuit. The signal further passes to the T1 transformer, which has three windings: primary broadcasting, primary receiving and secondary, connected to the network cable. Both primary windings are divided in a ratio of 1: 1. IO17 (Mac111) acts as a collision detector. If it only sends the LAN AT/XT board itself, the transformer transformer is balanced and the value of the comparator is "0". If another station broadcasts on the network at the same time, the transformer symmetry is violated and the "1" value appears at the comparator output.
The reception part consists of comparator IO18, monostable flip -flop IO16A, six -liter register IO14 and Memoirs of Prom IO15. The last two circuits act as a phase hinge and form a data separator.
On the board there is an eight-fold SW1 switch, which is used to select the TNS-Net 900 station number.