TDC-GPX acam messelectronic gmbh, TDC-GPX Datasheet - Page 51

• Manufacturer Part Number: TDC-GPX
• Description: Precision Time Interval Measurement
• Manufacturer: acam messelectronic gmbh

TDC-GPX
6 Bug Report
6.1 Data Bus: 16 Bit Mode
Subject:
CSN in 16-Bit mode
When working with a 16 Bit databus, register 14 Bit 4 = 1, there is a malfunction of CSN.
Relevance:
Systems with not only a TDC-GPX at the 16 Bit bus but other chips o TDCs connected too.
Description:
In 16 Bit mode we have two internal latches that collect the data for the high-word and the low-word and put them
together to one 28 bit value. Strobes on RDN or WRN toggle between the two latches. This should be deactived
when CSN is high but it is not.
As long as CSN is high no data are written in the TDC-GPX but the latches are toggled. If CSN goes low and the
pointer is already on the high-word latch then the data with the next RDN/WRN strobe will be wrong.
Workaround:
1. By Software
The following sequence at the beginning of any communication with the TDC-GPX will guarantee that the pointer
shows to the low-word latch:
Write Adr = 15, Val = 0x00 (empty address)
Write Adr = 14, Val = 0x00
Write Adr = 14, Val = 0x00 now the 16 Bit mode is definitely off, latch pointers are correct
Write Adr = 14, Val = 0x10 Switch on 16 Bit mode again
2. By Hardware
Disable the RDN/WRN lines with CSN = High
acam-messelectronic gmbh - Am Hasenbiel 27 - D-76297 Stutensee-Blankenloch - Germany - www.acam.de
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