T34VG1
The T34VG1 (Т34ВГ1 in Cyrillic) is a custom chip performing a similar role to that of the ZX Spectrum ULA within various Eastern European Spectrum clones, most notably the Didaktik M.
It is also sometimes labelled as a КА1515ХМ1-216 or as just ULA1.
Systems using this chip are typically clocked at 4 MHz. The chip uses the same scheme as the Amstrad CPC for sharing memory bandwidth between the CPU and video display engine, in that it introduces wait T-states (Tw states) by means of the Z80's WAIT pin, so that memory accesses are aligned to groups of four clock cycles, resulting in execution of between 3–4 million T-states per second depending on the instructions that are executed. Wait states are inserted regardless of the memory or I/O address being accessed, and are inserted even whilst the border is being drawn and during vertical retrace, so as to provide consistent CPU performance. This consistency is needed, for example, when executing the ROM's beeper and tape routines, as instruction fetches from ROM are also subject to wait states.
As the pixel clock is twice the CPU clock at 8 MHz, rather than the ~7 MHz pixel clock of the Spectrum, the screen is narrow in appearance.
It was used in a variety of computers, as well as the Belarusian "ALF TV Game" console.
Computers using the T34VG1 include:
- Anbelo/C
- Atas 128
- Atas 256
- Byte (Moldova, not Belarus)
- Companion M
- Companion 2
- Delta-micro
- Didaktik M
- Didaktik Kompakt
- Forum BK-09
- Forum BK-09 Turbo
- Quantum (Kvant) BK
- Quantum (Kvant) BK MC0530
- Iskra 1085
- Master
- Master 2
- Pik
- PLM-X
- Radon Plus
- Raton-9003 (early model)
- Sinko-Best
- Sirius
- Spektr B-IK
- Sura-S
- Symbol 48
- Symbol 128
- Vesta IK-31
Pinout
The pinout of the T34VG1 is given below. Note that pin 1 is in the centre of the lower row of pins and has a notch, and is immediately to the right of pin 64. Pins 8 and 9 are in the lower-right corner, pins 24 and 25 in the upper-right corner, pins 40 and 41 in the upper-left corner and pins 56 and 57 in the lower-left corner.
Pin | Name |
---|---|
1 | KEY1 |
2 | KEY2 |
3 | D0 |
4 | D1 |
5 | KEY3 |
6 | D2 |
7 | D3 |
8 | KEY4 |
9 | KEY5 |
10 | B |
11 | R |
12 | G |
13 | T0 |
14 | D4 |
15 | S0 |
16 | D5 |
17 | D6 |
18 | Y |
19 | TI |
20 | D7 |
21 | INT |
22 | M1 |
23 | IORQ |
24 | RFSH |
25 | WR |
26 | SSWR |
27 | SSRD |
28 | MREQ |
29 | RD |
30 | WE |
31 | CLK |
32 | 0V |
33 | CLK_IN |
34 | WAIT |
35 | CAS |
36 | CE |
37 | A7 |
38 | A15 |
39 | A6 |
40 | RAS |
41 | A14 |
42 | A12 |
43 | S |
44 | AR7 |
45 | AR6 |
46 | AR4 |
47 | A0 |
48 | AR3 |
49 | A4 |
50 | AR0 |
51 | A3 |
52 | AR2 |
53 | AR1 |
54 | AR5 |
55 | A2 |
56 | A1 |
57 | A13 |
58 | A10 |
59 | A8 |
60 | A11 |
61 | A9 |
62 | A5 |
63 | RST |
64 | Vcc |