T34VG1: Difference between revisions

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(ROM probably *is* contended, /CE is an output)
(Add companion 3, note existence of other chips in the КА1515ХМ1 family)
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* Companion M
* Companion M
* Companion 2
* Companion 2
* Companion 3
* Delta-micro
* Delta-micro
* Didaktik M
* Didaktik M
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* Symbol 128
* Symbol 128
* Vesta IK-31
* Vesta IK-31
There are similar chips which should not be confused with the T34VG1.  For example, the КА1515ХМ1-458 and КА1515ХМ1-433 are used together in the Infoton-030, a 128K clone, and the КА1515ХМ1-6004 is used in another 128K clone, the HIMAC 128.  There are also many other chips designated as some form of КА1515ХМ1 that are not related to the Spectrum, for example, a set of support chips for the UKNC, a clone of the PDP-11.


== Pinout ==
== Pinout ==

Revision as of 18:06, 29 August 2015

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 for access to any memory address, and for access to the ULA port ("port 0xfe"). These wait states are inserted as needed 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
  • Companion 3
  • 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

There are similar chips which should not be confused with the T34VG1. For example, the КА1515ХМ1-458 and КА1515ХМ1-433 are used together in the Infoton-030, a 128K clone, and the КА1515ХМ1-6004 is used in another 128K clone, the HIMAC 128. There are also many other chips designated as some form of КА1515ХМ1 that are not related to the Spectrum, for example, a set of support chips for the UKNC, a clone of the PDP-11.

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.

AR0–AR7 are multiplexed DRAM address lines. Data bus resistors may be required simply to provide the T34VG1 with electrical protection from the Z80, but details of this are not yet clear.

The T34VG1 is decodes writes to port 0x5f which it signals using SSWR and reads from port 0x1f which it signals using SSRD. It is speculated that both of these may simply decode A5, looking for it to go low.

The T34VG1 provides CE as an output, which indicates whether an address within the ROM range (0x0000–0x3fff) is being accessed.

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

See also