Data Sheet
ADuC7019/20/21/22/24/25/26/27/28/29
NONVOLATILE FLASH/EE MEMORY
The ADuC7019/20/21/22/24/25/26/27/28/29 incorporate
Flash/EE memory technology on-chip to provide the user with
nonvolatile, in-circuit reprogrammable memory space.
Retention quantifies the ability of the Flash/EE memory to
retain its programmed data over time. Again, the parts are
qualified in accordance with the formal JEDEC Retention
Lifetime Specification (A117) at a specific junction temperature
(TJ = 85°C). As part of this qualification procedure, the
Flash/EE memory is cycled to its specified endurance limit,
described in Table 1, before data retention is characterized. This
means that the Flash/EE memory is guaranteed to retain its data
for its fully specified retention lifetime every time the Flash/EE
memory is reprogrammed. In addition, note that retention
lifetime, based on an activation energy of 0.6 eV, derates with TJ
as shown in Figure 61.
Like EEPROM, flash memory can be programmed in-system
at a byte level, although it must first be erased. The erase is
performed in page blocks. As a result, flash memory is often
and more correctly referred to as Flash/EE memory.
Overall, Flash/EE memory represents a step closer to the
ideal memory device that includes nonvolatility, in-circuit
programmability, high density, and low cost. Incorporated in
the ADuC7019/20/21/22/24/25/26/27/28/29, Flash/EE memory
technology allows the user to update program code space in-
circuit, without the need to replace one-time programmable
(OTP) devices at remote operating nodes.
600
Each part contains a 64 kB array of Flash/EE memory. The
lower 62 kB is available to the user and the upper 2 kB contain
permanently embedded firmware, allowing in-circuit serial
download. These 2 kB of embedded firmware also contain a
power-on configuration routine that downloads factory-
calibrated coefficients to the various calibrated peripherals
(such as ADC, temperature sensor, and band gap references).
This 2 kB embedded firmware is hidden from user code.
450
300
150
0
Flash/EE Memory Reliability
30
40
55
70
85
100
125
135
150
JUNCTION TEMPERATURE (°C)
The Flash/EE memory arrays on the parts are fully qualified for
two key Flash/EE memory characteristics: Flash/EE memory
cycling endurance and Flash/EE memory data retention.
Figure 61. Flash/EE Memory Data Retention
PROGRAMMING
Endurance quantifies the ability of the Flash/EE memory to be
cycled through many program, read, and erase cycles. A single
endurance cycle is composed of four independent, sequential
events, defined as
The 62 kB of Flash/EE memory can be programmed in-circuit,
using the serial download mode or the provided JTAG mode.
Serial Downloading (In-Circuit Programming)
1. Initial page erase sequence
2. Read/verify sequence (single Flash/EE)
3. Byte program sequence memory
The ADuC7019/20/21/22/24/25/26/27/28/29 facilitate code
download via the standard UART serial port or via the I2C port.
The parts enter serial download mode after a reset or power
cycle if the BM pin is pulled low through an external 1 kΩ
resistor. After a part is in serial download mode, the user can
download code to the full 62 kB of Flash/EE memory while
the device is in-circuit in its target application hardware. An
executable PC serial download is provided as part of the
development system for serial downloading via the UART.
The AN-806 Application Note describes the protocol for
serial downloading via the I2C.
4. Second read/verify sequence (endurance cycle)
In reliability qualification, every half word (16-bit wide)
location of the three pages (top, middle, and bottom) in the
Flash/EE memory is cycled 10,000 times from 0x0000 to
0xFFFF. As indicated in Table 1, the Flash/EE memory
endurance qualification is carried out in accordance with
JEDEC Retention Lifetime Specification A117 over the
industrial temperature range of −40° to +125°C. The results
allow the specification of a minimum endurance figure over a
supply temperature of 10,000 cycles.
JTAG Access
The JTAG protocol uses the on-chip JTAG interface to facilitate
code download and debug.
Rev. F | Page 51 of 104
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