ACE1502 Datasheet, PDF (23/33 Pages) Fairchild Semiconductor – Arithmetic Controller Engine for Low Power Applications

10. In-circuit Programming Specification
The ACEx microcontroller supports in-circuit programming of
the internal data EEPROM, code EEPROM, and the initializa-
tion registers.
In order to enter into program mode a 10-bit opcode (0x34B)
must be shifted into the ACE1502 while the device is executing
the internal power on reset (T_RESET). The shifting protocol fol-
lows the same timing rules as the programming protocol defined
in Figure 30.
SHIFT_OUT pin. It is recommended that the external program-
mer samples this signal t _ACCESS (500 ns) after the rising edge
of the CLOCK signal. The serial response word, sent immedi-
ately after entering programming mode, contains indeterminate
data.
After 32 bits have been shifted into the device, the external pro-
grammer must set the LOAD signal to 0V, and then apply two
clock pulses as shown in Figure 30 to complete program cycle.
The opcode is shifted into the ACE1502 serially, MSB first, with
the data being valid by the rising edge of the clock. Once the
pattern is shifted into the device, the current 10-bit pattern is
matched to protocol entrance opcode of 0x34B. If the 10-bit
pattern is a match, the device will enable the internal program
mode flag so that the device will enter into program mode once
reset has completed (see Figure 30.)
The opcode must be shifted in after Vcc settles to the nominal
level and should end before the power on reset sequence
(T_reset) completes; otherwise, the device will start normal
execution of the program code. If the external reset is applied by
bringing the reset pin low, once the reset pin is release the
opcode may now be shifted in and again should end before the
reset sequence completes.
10.3 Programming Protocol
After placing the device in program, the programming protocol
and commands may be issued.
An externally controlled four-wire interface consisting of a LOAD
control pin (G3), a serial data SHIFT-IN input pin (G4), a serial
data SHIFT-OUT output pin (G2), and a CLOCK pin (G1) is
used to access the on-chip memory locations. Communication
between the ACEx microcontroller and the external programmer
is made through a 32-bit command and response word
described in Table 14. Be sure to either float or tie G5 to Vcc for
proper programming functionality.
The serial data timing for the four-wire interface is shown in Fig-
ure 31 and the programming protocol is shown in Figure 30.
10.3.1 Write Sequence
The external programmer brings the ACEx microcontroller into
programming then needs to set the LOAD pin to Vcc before
shifting in the 32-bit serial command word using the SHIFT_IN
and CLOCK signals. By definition, bit 31 of the command word
is shifted in first. At the same time, the ACEx microcontroller
shifts out the 32-bit serial response to the last command on the
The SHIFT_OUT pin acts as the handshaking signal between
the device and programming hardware once the LOAD signal is
brought low. The device sets SHIFT_OUT low by the time the
programmer has sent the second rising edge during the LOAD
= 0V phase (if the timing specifications in Figure 30 are
obeyed).
The device will set the R bit of the Status register when the write
operation has completed. The external programmer must wait
for the SHIFT_OUT pin to go high before bringing the LOAD sig-
nal to Vcc to initiate a normal command cycle.
10.3.2 Read Sequence
When reading the device after a write, the external programmer
must set the LOAD signal to Vcc before it sends the new com-
mand word. Next, the 32-bit serial command word (for during a
READ) should be shifted into the device using the SHIFT_IN
and the CLOCK signals while the data from the previous com-
mand is serially shifted out on the SHIFT_OUT pin. After the
Read command has been shifted into the device, the external
programmer must, once again, set the LOAD signal to 0V and
apply two clock pulses as shown in Figure 30 to complete
READ cycle. Data from the selected memory location, will be
latched into the lower 8 bits of the command word shortly after
the second rising edge of the CLOCK signal.
Writing a series of bytes to the device is achieved by sending a
series of Write command words while observing the devices
handshaking requirements.
Reading a series of bytes from the device is achieved by send-
ing a series of Read command words with the desired
addresses in sequence and reading the following response
words to verify the correct address and data contents.
The addresses of the data EEPROM and code EEPROM
locations are the same as those used in normal operation.
Powering down the device will cause the part to exit program-
ming mode.
Table 14 32-Bit Command and Response Word
Bit Number
Input Command Word
Output Response Word
bits 31-30
bit 29
bit 28
bits 27-25
bit 24
bits 23-19
bits 18 -8
bits 7-0
Must be set to 0
X
Set to 1 to read/write data EEPROM, or the initialization X
registers, otherwise 0
Set to 1 to read/write code EEPROM, otherwise 0
X
Must be set to 0
X
Set to 1 to read, 0 to write
X
Must be set to 0
X
Address of the byte to be read or written
Same as Input command word
Data to be programmed or zero if data is to be read
Programmed data or data read at specified address
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ACE1502 Product Family Rev. 1.7
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