This section lists the exchange between Rakewell and LYONTEK to find out why the RAM chip fails.
LYONTEK - LY62W10248ML-55LLI - SRAM, 8M, 1MX8, 2.7-5.5V, 44TSOPII
This memory chip is a 'drop-in' replacement for the BSI chip (see below).
TESTED FAILS when loading a file in PipeDream.
Manufacture response:-
We have read the information on web-site provided from customer. Just as customer said, yes, the circuit diagram is pretty straightforward. We can not find an problem from that. Just we know, the major differences between our parts and BSI's are the design on ESD protection devices, shown as below. We use type 2 on our parts, but BSI uses type 1 without using P-diode,Dp. We wondered if this could be the issue. Maybe, we need to make some tests on customer's AP board to learn the real situations.
My response :-
Sorry about the delay in replying but I have been comparing the specs between both these chips and running more tests.
Where do we go from here?
I just can’t believe it is a timing issue because the Z80 is running at 3.2768 Mhz. A read or write command takes 3 clock cycles. This gives 915.52734375 nS and the device only needs 55.
How can we test and see what is happening? Have you got any suitable test equipment?
Manufacture response:-
Lyontek really wants to realize what happened. We will do our best to find out the issues as Vic would offer his supports, providing measurement results on application boards.
After reading Vic's information and thinking over, I supposed that the major differences I reported, design on ESD protection diodes, could be the issue. The protection diode may limit the trigger voltage in the input nodes to be less than Vcc+0.6V. Hence, I try to check if there exists any input voltage for Flash Memory which is quite over Vcc. The following comes from datasheet of AM29F080B-90ED, in the page 10. I guess that it could be an issue on Lyontek's parts as the function of Auto-select Mode is executed because the trigger voltage on A9 is limited by ESD protection diode, less than Vcc+5.6V.
My response
Note: FYI The Z88 has 3 slots for these cards. It can only program EPROMs using the 12v line in slot 3. The RAM fails when the card is in Slot 1, there is no 12v line available there. We do use the auto-select mode to see what Flash chip is present on the card. We also program the Flash chip. We do not use the higher voltage to do these functions. We use the alternative mode so that we can program the card in any slot using 5v. I can confirm that I have programmed the Flash Chip and read it. The card does not fail when I do that.
The Z88 recognizes that it has RAM. I have a simple RAM test, which passes.
I have uncompressed files, and have saved files to the flash chip. The failure occurs when I am loading a larger file into the word-processor. The Z88 displays a “fail” message which is associated to a memory failure of some sort (usually if the RAM is removed from the slot).
Technical Spec of a Flash and RAM chips
| Z80 4MHz | AS6C8008 | ||||||
|---|---|---|---|---|---|---|---|
Supply Voltage Min | V | 2.4 | 2.7 | 2.7 | 4.5 | ||
| Supply Voltage Typ | V | - | 3.0 | 3.0 | 5.0 | ||
| Supply Voltage Max | V | 5.5 | 5.5 | 5.5 | 5.5 | ||
Input High Voltage | V | 2.2 to VCC | 0.7 x VCC min to VCC+0.3 | 2.2 to VCC+0.3 | 2.4 to VCC+0.3 | 2.4 to VCC+0.5 | 2.2 to VCC + 0.5 V |
Input Low Voltage | V | -0.3 to 0.8 | 0.5 to 0.8 | -0.5 to 0.8 | - 0.2 to 0.6 | - 0.2 to 0.6 | –0.5 to 0.8 |
Output High Voltage | V | 2.4 min | 0.85 x VCC | 2.4 min | 2.4 min | 2.4 min | |
Output Low Voltage | V | 0.4 max | 0.45 | 0.4 max | 0.4 max | 0.4 max | |
Standby Power | uA | 1 | 3.5 to 50 | 6 to 80 | 10 to 50 | 2 to 8 | |
| Power Consumption | mA | 20 - 40 | 39 | 60 | 30 to 60 | 1.8 to 3 | |
VCC for Data Retention | V | 1.5 | 2.0 | 1.5 | 2.0 | ||
| Read Timings | |||||||
| Read Cycle Time tRC | ns | 55 min | 55 min | 55 min | 55 min | 45 min | |
| Address Access Time tAA | 55 min | 55 max | 55 max | 55 max | 45 max | ||
Chip Enable Access Time tACE | 55 min | 55 max | 55 max | 55 max | 45 max | ||
| Output Enable Access Time tOE | 30 max | 25 max | 30 max | 30 max | 22 max | ||
| Chip Enable to Output in Low-Z tCLZ | 18 min | 10 min | 10 min | 10 min | 5 min | ||
| Output Enable to Output in Low-Z tOLZ | 18 min | 10 min | 5 min | 5 min | 10 min | ||
| Chip Disable to Output in High-Z tCHZ | 30 max | 20 max | 20 max | 18 max | |||
Output Disable to Output in High-Z tOHZ | 25 max | 20 max | 20 max | 18 max | |||
Output Hold from Address Change tOH | 0 | 10 min | 10 min | 10 min | 10 min | ||
| Write Timings | |||||||
Write Cycle Time tWC | 55 min | 55 min | 55 min | 55 min | 45 min | ||
Address Valid to End of Write tAW | 40 min | 40 min | 50 min | 50 min | 35 min | ||
Chip Enable to End of Write tCW | 0 | 50 min | 50 min | 35 min | |||
Address Set-up Time tAS | 0 | 40 min | 0 | 0 | 35 min | ||
Write Pulse Width tWP | 20 min | 30 min | 45 min | 45 min | 35 min | ||
Write Recovery Time tWR | 0 | 0 | 0 | 0 | |||
Data to Write Time Overlap tDW | 25 min | 25 min | 25 min | 25 min | 25 min | ||
Data Hold from End of Write Time tDH | 0 | 0 | 0 | 0 | 0 | ||
Data Setup to Write End | 25 min | ||||||
Output Active from End of Write tOW | 5 min | 5 min | 5 min | ||||
Write to Output in High-Z tWHZ | 25 max | 20 max | 20 max | 10 max | |||
| THE Z80 CPU : TIMING |
This is the exchange between Rakewell and LYONTEK to find out why their RAM chip fails.
LYONTEK - LY62W10248ML-55LLI - SRAM, 8M, 1MX8, 2.7-5.5V, 44TSOPII This memory chip should be a 'drop-in' replacement for the BSI chip. TESTED FAILS when loading a file in PipeDream. Manufacture response:-
My response :-
Manufacture response:-
|
My response
Note: FYI The Z88 has 3 slots for these cards. It can only program EPROMs using the 12v line in slot 3. The RAM fails when the card is in Slot 1, there is no 12v line available there. We do use the auto-select mode to see what Flash chip is present on the card. We also program the Flash chip. We do not use the higher voltage to do these functions. We use the alternative mode so that we can program the card in any slot using 5v. I can confirm that I have programmed the Flash Chip and read it. The card does not fail when I do that.
The Z88 recognizes that it has RAM. I have a simple RAM test, which passes.
I have uncompressed files, and have saved files to the flash chip. The failure occurs when I am loading a larger file into the word-processor. The Z88 displays a “fail” message which is associated to a memory failure of some sort (usually if the RAM is removed from the slot).