Carel Vedder HRG1

This expansion, compatible with both American and Japanese Model1's and the Video Genie I, II, EG 3003 and EG 3008 produces a 184 * 192 monochrome screen. When installed, it displays on the original TRS-80 screen. All timing is derived fromthe TRS-80. The Video memory, 12 KByte Static RAM, is controlled via six I/O ports, 0 to 5.

Port usage:

Port 0 disables the HRG1, port 1 enables it. Port 4 reads six bits from the HRG1 memory, port 5 writes six bits to the HRG1. Port 2 and 3 are used to program addressing:

    |           port 2             |           port 3             |
bit: 0   1   2   3   4   5   6   7   0   1   2   3   4   5   6   7
    |     64 char. hor.    | 16 reg. vert. | 12 pnts. vert.|      |

The extension to Basic BASGR gives eight extra commands:

The Basic extension BASGR was written for NEWDOS80 V2.0, and loaded from 5200H. It then positions itself in hi memory.

The hardware:

The schema has some interesting non-technical details:
"© RB Electronic Gmbh" is a German company. So, Carel Vedder didn't design the HRG1 themselves
The Text above reads "Repair shop scheme, do not give away".

The HRG board installed at the bottom of the Model 1

The HRG1 is connected to the TRS-80 with two flatcables: a 16 wire and a 24 wire cable. The HRG1 output is OR-ed with the original video signal. In this instance there is also an extra board connected with eight wires to the HRG.

The extra board connecting the HRG board to the Model 1

Last update: 2022-10-07