DSECASH Maxim Integrated Products, DSECASH Datasheet - Page 16

• Manufacturer Part Number: DSECASH
• Description: Power Management Modules & Development Tools eCash Evaluation Kit eCash Evaluation Kit
• Manufacturer: Maxim Integrated Products

Specifications of DSECASH

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPENDIX A: THE ECASH PROCESSOR
One of the purposes of the eCash processor is to offload the difficult 1-Wire SHA operations to a dedicated
microprocessor. The eCash processor on the eCash evaluation board utilizes the DS1963S in an internal 1-Wire
network to perform the SHA-1 authentication and signing of service data. This has speed advantages and also
securely keeps the secrets in a stainless steel iButton package.
Alternately, the firmware written in ‘C’ can be ported to many different processors. There are three main operating
modes to the eCash processor: Autonomous, Lock-Step, and Manual. Autonomous mode allows the eCash
processor to work without any interaction with the host processor. However, status information will be sent out the
serial interface when an event occurs. Lock-Step mode allows the eCash processor to do all of the 1-Wire
authentication and/or debiting work but allows the host to approve key steps in the process. Manual mode allows
the host to instruct the eCash processor to do any individual operation. The Manual mode commands can also be
used while the eCash processor is in Autonomous or Lock-Step mode.
Figure 16. eCash Processor Application Example
Speed considerations: Autonomous is the fastest, Lock-Step is next and full Manual mode is the slowest due to the
overhead constraint of serial communication before each 1-Wire operation.
Table 6. Mode Flags
Sequence
(and bit #)
0
1
2
3
4
5
6
7
(microprocessor)
Host System
Operation Description
Automatic 1-Wire polling for user token
Automatic read and authentication
Automatic debit
Automatic Pulse of I/O bit
Automatic update of the LCD
Enable Overdrive operation
not used
not used
Service Control Unit
Serial
Interface
Coprocessor
for DS1963S
16 of 21
eCash Evaluation Board
Internal
1-Wire
processor
Optional IO
eCash
Coprocessor
for DS1961S
External
1-Wire
DSECASH: eCash Evaluation Kit
iButton
Reader