1 this errata is applicable to the following devices: ? at89s8252 AT89LS8252 at89s53 at89ls53 with the following markings and needs to be used in conjunction with the correspond- ing device datasheets. regarding the in-system programming procedure, atmel currently recommends the following isp waveforms for implementing the isp programming algorithm in the at89s-series devices: these waveforms should be used in addition to the serial downloading waveforms shown in the respective device datasheets. at89s8252 24xx xxxx AT89LS8252 12xx xxxx at89s53 24xx xxxx at89ls53 12xx xxxx rst (>2 machine cycles) a (<1/2 machine cycle) (>1 machine cycle) sck 7 6 gnd v cc this glitch may occur in certain systems because when rst goes high, port 1 pins will be driven with a strong pullup for one clock cycle; if the glitch does occur, it can be interpreted incorrectly as the first sck pulse of a serial data stream. so the falling edge of rst at point a is necessary to ? clean-up ? the internal state machine. should be powered up and stable prior to the waveforms below) cc (v microcontrollers at89s8252 AT89LS8252 at89s53 at89ls53 errata sheet rev. 1486a ? 10/99
errata sheet 2 isp line driving contention the atmel at89s microcontrollers use three spi lines to implement in-system programming (isp). when the isp programmer asserts the reset line, the target at89s microcontroller is supposed to tri-state all i/o pins including the spi lines and then wait for commands from the pro- grammer. experiments using at89s devices have shown that if the user code writes to any of the isp i/o pins (mosi, miso, sck) within approximately 500 ms of the user code coming out of reset condition, any subsequent serial programming operation fails. the problem is then that the only way to re-program the device successfully is to physically remove it from the target board and erase it in a parallel programmer. the solution make sure that the user code does not access any of the isp i/o pins within 500 ms of coming out of reset condition.
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