Method and apparatus for concealing the enablement of a device by modifying a status word
US5218683A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 24, 1992 |
| Grant date | Jun 8, 1993 |
| Priority date | — |
| Expiry date | Apr 24, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F13/126
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A status word modification device. A serial communications device (11) contains two universal asynchronous receiver transmitters (UARTs) (14, 15). Each UART contains a first in, first out (FIFO) buffer (14a), two status buffers (14b, 14c), and a FIFO control register (14d). If the applications program in the host (10) is an enhanced application program which supports the use of the FIFO buffer (14a), then the program will cause FIFO enablement instructions to be written into the control register (14d). In this case, the interface circuit (22) allows the status words to pass unaltered whenever the host (10) reads the status buffers (14b, 14c). However, if the applications program is a standard applications program which does not support the use of the FIFO buffer (14a), then the program will not write to the control register (14d). In this case, the interface circuit (22) will alter the value of selected bits of the status words if the user has enabled the FIFO buffer (14a) and the host reads the status buffers (14b, 14c). The alteration of the status word prevents the standard applications program from treating the FIFO-related bits in the status words as data errors.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.