
HMS9xC7132 / HMS9xC7134
74
May.2001 ver1.1
Encryption Array
Within the EPROM array are 64bytes of Encryption Array that
are initially unprogrammed (all 1s). Every time that a byte ad-
dressed during a verify, address line are used to select a byte of
the Encryption array. This byte is then exclusive NOR-ed
(XNOR) with the code byte, creating an Encrypted Verify byte.
The algorithm, with the array in the unprogrammed state (all 1s),
will return the code in its original, unmodified form. It is recom-
mended that whenever the Encryption Array is used, at least one
of the Lock Bits be programmed as well.
Reading the Signature Bytes
The HMS97C7132 signature bytes in location 30H and 20H. To read these bytes follow the procedure for EPROM verify, except that P3.6
and P3.7 need to be pulled to a logic low.
Table 21-3 The Value
Quick-pulse programming
The setup for micro-controller quick-pulse programming is
shown in Figure 21-2. Note that the HMS97C7132 is running
with a 4 to 6MHz oscillator. The reason the oscillator needs to be
running is that the device is executing internal address and pro-
gram data transfers.
The address of the EPROM location to be programmed is applied
to port 1, 2 and VSYNCIN, as shown in Figure 21-1. The code
byte to be programmed into that location is applied to port 0. RE-
SET, PSEN and pins of port2 and 3 in Table 21.1 are held at the
“Program Code Data” levels indicated in Table 21.1. The P3.5/
PROG is pulsed low 10 times as shown Figure 21-2.
To program the encryption table, repeat the 10 pulses program-
ming sequence for address 0 through 3F H, using the “Program
Encryption Table” levels. Do not forget that after the encryption
table is programmed, verification cycle will produce only en-
crypted data.
To program the security bits, repeat the 10 pulses programming
sequence using the “Program Security Bit” levels. After one se-
curity bit is programmed, further programming of the code mem-
ory and encryption table is disabled. However, the other security
bit can still be programmed. Note that INT0/VPP pin must not be
allowed to go above the maximum specified VPP level for any
amount of time. Even a narrow glitch above that voltage can
cause permanent damage to the device.
The VPP source should be well regulated and free glitches and
overshoot.
Remarks
Device
Device ID
Manufacturer ID
Location
20H
30H
HMS97C7132
Contents
68H
ADH