27128-pinout 16K x 8 ROM pinout
DIP-28. 16K x 8 ROM or EPROM in the JEDEC 27128 pinout.
HERO Jr: the two 16K x 8 monitor ROMs. U207 is 444-283 and U208 is 444-254; errata notice 591-4523 revises both. The decoder U202 selects them across $8000-$BFFF and $E000-$FFFF (U208). A bad ROM gives a robot that will not boot, or a boot that stops at the same point each time. Check the errata revision before swapping.
Open the interactive 27128 ROM pinoutPins
| Pin | Name | Type | Signal |
|---|---|---|---|
| 1 | VPP | power | Programming voltage. Tie to Vcc in normal use. |
| 2 | A12 | addr | Address bit 12. |
| 3 | A7 | addr | Address bit 7. |
| 4 | A6 | addr | Address bit 6. |
| 5 | A5 | addr | Address bit 5. |
| 6 | A4 | addr | Address bit 4. |
| 7 | A3 | addr | Address bit 3. |
| 8 | A2 | addr | Address bit 2. |
| 9 | A1 | addr | Address bit 1. |
| 10 | A0 | addr | Address bit 0. |
| 11 | D0 | data | Data bit 0. |
| 12 | D1 | data | Data bit 1. |
| 13 | D2 | data | Data bit 2. |
| 14 | GND | ground | Ground. |
| 15 | D3 | data | Data bit 3. |
| 16 | D4 | data | Data bit 4. |
| 17 | D5 | data | Data bit 5. |
| 18 | D6 | data | Data bit 6. |
| 19 | D7 | data | Data bit 7. |
| 20 | /CE | ctrl | Chip enable, active low. |
| 21 | A10 | addr | Address bit 10. |
| 22 | /OE | ctrl | Output enable, active low. |
| 23 | A11 | addr | Address bit 11. |
| 24 | A9 | addr | Address bit 9. |
| 25 | A8 | addr | Address bit 8. |
| 26 | A13 | addr | Address bit 13. |
| 27 | /PGM | ctrl | Program pulse. Not used in reading; tie high. (A14 on the 27256.) |
| 28 | VCC | power | +5 V supply. |
Fitted in
- HERO Jr U207, U208
- Commodore 1541 disk drive UA2 (1541C, 251968-01), U4 (1541-II, 251968-03 / 355640-01)
- Atari 800XL U5, OS ROM 16K x 8 (C061598-29 on the photographed board). The FSM schematic draws a 27128 with pins 1 (VPP) and 27 (PGM) at +5 V.
- BBC Micro Model B IC51 (MOS), IC52 (BASIC), IC100, IC101 (sideways)
- BBC Master 128 IC27 (16K socket, ROM 8)